[PATCH v6 0/6] Add --dhcp-boot and --dhcp-opt options

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[PATCH v3 0/2] [PATCH 0/2] dhcpv6:...

Anshu Kumari

24 Aug 2026 24 Aug '26

3:44 p.m.

This series adds support for custom DHCP options in passt, enabling network boot (PXE/UEFI HTTP Boot) and arbitrary DHCP option injection. Two new command-line flags are introduced: --dhcp-boot URL Sets the boot file URL (DHCP option 67 and the legacy boot file field) --dhcp-opt CODE,VALUE Sets any DHCP option by numeric code, with type-aware parsing per RFC 2132 The DHCP reply path is extended with option overload support (RFC 2132 option 52), allowing options to overflow into the file and sname fields when the standard options area is full. RFC 3396 option splitting for concatenation-requiring options has also been introduce as a separate patch. Anshu Kumari (6): dhcp: Refactor fill_one() to operate on a generic buffer dhcp: Add option state management with enum opt_state dhcp: Add option overload dhcp: Add --dhcp-opt with option table and value parser dhcp: Add --dhcp-boot command-line option dhcp: Add RFC 3396 option splitting for concatenation-requiring options conf.c | 31 +++- dhcp.c | 561 ++++++++++++++++++++++++++++++++++++++++++++++++++------ dhcp.h | 2 + passt.1 | 49 +++++ 4 files changed, 588 insertions(+), 55 deletions(-) -- 2.55.0

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Anshu Kumari

24 Aug 24 Aug

3:44 p.m.

New subject: [PATCH v6 1/6] dhcp: Refactor fill_one() to operate on a generic buffer

Change fill_one() to accept a buffer pointer and capacity instead of a struct msg pointer. This is a pure refactor with no behavior change, preparing for option overload support where fill_one() will also write into the file and sname fields. Link: https://bugs.passt.top/show_bug.cgi?id=192 Signed-off-by: Anshu Kumari --- v6: - no changes. v5: - Restore debug messages for skipped options in fill() - Add /* code and length of option */ comment in size check - Use buf + *offset instead of &buf[*offset] for memcpy v3: - Restored removed comments: "If we don't have space to write the option, then just skip" and "Move to option". v2: - Renamed parameter cap → size. --- dhcp.c | 27 ++++++++++++++------------- 1 file changed, 14 insertions(+), 13 deletions(-) diff --git a/dhcp.c b/dhcp.c index c3c7422..bb72b72 100644 --- a/dhcp.c +++ b/dhcp.c @@ -131,28 +131,29 @@ struct msg { } __attribute__((__packed__)); /** - * fill_one() - Fill a single option in message - * @m: Message to fill + * fill_one() - Fill a single option into a buffer + * @buf: Buffer to write option + * @size: Usable size of @buf (excluding end marker) * @o: Option number - * @offset: Current offset within options field, updated on insertion + * @offset: Current offset within @buf, updated on insertion * - * Return: false if m has space to write the option, true otherwise + * Return: false if @buf has space to write the option, true otherwise */ -static bool fill_one(struct msg *m, int o, int *offset) +static bool fill_one(uint8_t *buf, size_t size, int o, int *offset) { size_t slen = opts[o].slen; /* If we don't have space to write the option, then just skip */ - if (*offset + 2 /* code and length of option */ + slen > OPT_MAX) + if (*offset + 2 /* code and length of option */ + slen > size) return true; - m->o[*offset] = o; - m->o[*offset + 1] = slen; + buf[*offset] = o; + buf[*offset + 1] = slen; /* Move to option */ *offset += 2; - memcpy(&m->o[*offset], opts[o].s, slen); + memcpy(buf + *offset, opts[o].s, slen); opts[o].sent = 1; *offset += slen; @@ -177,19 +178,19 @@ static int fill(struct msg *m) * Put it there explicitly, unless requested via option 55. */ if (opts[55].clen > 0 && !memchr(opts[55].c, 53, opts[55].clen)) - if (fill_one(m, 53, &offset)) - debug("DHCP: skipping option 53"); + if (fill_one(m->o, OPT_MAX, 53, &offset)) + debug("DHCP: skipping option 53"); for (i = 0; i < opts[55].clen; i++) { o = opts[55].c[i]; if (opts[o].slen != -1) - if (fill_one(m, o, &offset)) + if (fill_one(m->o, OPT_MAX, o, &offset)) debug("DHCP: skipping option %i", o); } for (o = 0; o < 255; o++) { if (opts[o].slen != -1 && !opts[o].sent) - if (fill_one(m, o, &offset)) + if (fill_one(m->o, OPT_MAX, o, &offset)) debug("DHCP: skipping option %i", o); } -- 2.55.0

Anshu Kumari

3:44 p.m.

New subject: [PATCH v6 2/6] dhcp: Add option state management with enum opt_state

Overloading slen = -1 to mean "not set" conflates the option length with its lifecycle state, and can't express additional states such as "set by the user via command-line" which will be needed for --dhcp-opt support. Introduce enum opt_state with OPT_UNSET (option not configured) and OPT_DEFAULT (derived from host configuration). Replace all slen = -1 / slen != -1 checks with state comparisons, and set state = OPT_DEFAULT for options initialised in dhcp_init() and at reply time in dhcp(). Link: https://bugs.passt.top/show_bug.cgi?id=192 Signed-off-by: Anshu Kumari --- v6: - Rewrote commit message to explain why slen = -1 overloading is problematic and how it motivates the enum. - Dropped explicit OPT_UNSET initialization loop inside dhcp_init(). - Realigned opts[51] initializer for consistency. v5: - New patch: introduce enum opt_state { OPT_UNSET, OPT_DEFAULT } to replace slen = -1 for tracking option state - Replace all slen = -1 / slen != -1 checks with state = OPT_UNSET / state != OPT_UNSET - Set OPT_DEFAULT for options initialised in dhcp_init() and at reply time --- dhcp.c | 58 ++++++++++++++++++++++++++++++++++++++-------------------- 1 file changed, 38 insertions(+), 20 deletions(-) diff --git a/dhcp.c b/dhcp.c index bb72b72..321968a 100644 --- a/dhcp.c +++ b/dhcp.c @@ -33,13 +33,24 @@ #include "log.h" #include "dhcp.h" +/** + * enum opt_state - DHCP option state + * @OPT_UNSET: Option not configured + * @OPT_DEFAULT: Option derived from host configuration + */ +enum opt_state { + OPT_UNSET = 0, + OPT_DEFAULT, +}; + /** * struct opt - DHCP option * @sent: Convenience flag, set while filling replies - * @slen: Length of option defined for server, -1 if not going to be sent + * @slen: Length of option defined for server * @s: Option payload from server * @clen: Length of option received from client, -1 if not received * @c: Option payload from client + * @state: Option state (unset or default) */ struct opt { int sent; @@ -47,6 +58,7 @@ struct opt { uint8_t s[255]; int clen; uint8_t c[255]; + enum opt_state state; }; static struct opt opts[256]; @@ -73,19 +85,17 @@ static struct opt opts[256]; */ void dhcp_init(void) { - int i; - - for (i = 0; i < ARRAY_SIZE(opts); i++) - opts[i].slen = -1; - - opts[1] = (struct opt) { 0, 4, { 0 }, 0, { 0 }, }; /* Mask */ - opts[3] = (struct opt) { 0, 4, { 0 }, 0, { 0 }, }; /* Router */ - opts[51] = (struct opt) { 0, 4, { 0xff, - 0xff, - 0xff, - 0xff }, 0, { 0 }, }; /* Lease time */ - opts[53] = (struct opt) { 0, 1, { 0 }, 0, { 0 }, }; /* Type */ - opts[54] = (struct opt) { 0, 4, { 0 }, 0, { 0 }, }; /* Server ID */ + /* Mask */ + opts[1] = (struct opt) { 0, 4, { 0 }, 0, { 0 }, OPT_DEFAULT, }; + /* Router */ + opts[3] = (struct opt) { 0, 4, { 0 }, 0, { 0 }, OPT_DEFAULT, }; + /* Lease time */ + opts[51] = (struct opt) { 0, 4, { 0xff, 0xff, 0xff, 0xff }, + 0, { 0 }, OPT_DEFAULT }; + /* Type */ + opts[53] = (struct opt) { 0, 1, { 0 }, 0, { 0 }, OPT_DEFAULT, }; + /* Server ID */ + opts[54] = (struct opt) { 0, 4, { 0 }, 0, { 0 }, OPT_DEFAULT, }; } /** @@ -183,13 +193,13 @@ static int fill(struct msg *m) for (i = 0; i < opts[55].clen; i++) { o = opts[55].c[i]; - if (opts[o].slen != -1) + if (opts[o].state != OPT_UNSET) if (fill_one(m->o, OPT_MAX, o, &offset)) debug("DHCP: skipping option %i", o); } for (o = 0; o < 255; o++) { - if (opts[o].slen != -1 && !opts[o].sent) + if (opts[o].state != OPT_UNSET && !opts[o].sent) if (fill_one(m->o, OPT_MAX, o, &offset)) debug("DHCP: skipping option %i", o); } @@ -243,6 +253,7 @@ static void opt_set_dns_search(const struct ctx *c, size_t max_len) int i; opts[119].slen = 0; + opts[119].state = OPT_DEFAULT; for (i = 0; i < 255; i++) max_len -= opts[i].slen; @@ -291,7 +302,7 @@ static void opt_set_dns_search(const struct ctx *c, size_t max_len) } if (!opts[119].slen) - opts[119].slen = -1; + opts[119].state = OPT_UNSET; } /** @@ -389,7 +400,7 @@ int dhcp(const struct ctx *c, struct iov_tail *data) iov_drop_header(data, *olen); } - opts[80].slen = -1; + opts[80].state = OPT_UNSET; if (opts[53].clen > 0 && opts[53].c[0] == DHCPDISCOVER) { if (opts[80].clen == -1) { info("DHCP: offer to discover"); @@ -398,6 +409,7 @@ int dhcp(const struct ctx *c, struct iov_tail *data) info("DHCP: ack to discover (Rapid Commit)"); opts[53].s[0] = DHCPACK; opts[80].slen = 0; + opts[80].state = OPT_DEFAULT; } } else if (opts[53].clen <= 0 || opts[53].c[0] == DHCPREQUEST) { info("%s: ack to request", /* DHCP needs a valid message type */ @@ -421,6 +433,7 @@ int dhcp(const struct ctx *c, struct iov_tail *data) != (c->ip4.guest_gw.s_addr & mask.s_addr)) { /* a.b.c.d/32:0.0.0.0, 0:a.b.c.d */ opts[121].slen = 14; + opts[121].state = OPT_DEFAULT; opts[121].s[0] = 32; memcpy(opts[121].s + 1, &c->ip4.guest_gw, sizeof(c->ip4.guest_gw)); @@ -430,6 +443,7 @@ int dhcp(const struct ctx *c, struct iov_tail *data) if (c->mtu) { opts[26].slen = 2; + opts[26].state = OPT_DEFAULT; opts[26].s[0] = c->mtu / 256; opts[26].s[1] = c->mtu % 256; } @@ -441,12 +455,15 @@ int dhcp(const struct ctx *c, struct iov_tail *data) ((struct in_addr *)opts[6].s)[i] = c->ip4.dns[i]; opts[6].slen += sizeof(uint32_t); } - if (!opts[6].slen) - opts[6].slen = -1; + if (opts[6].slen) + opts[6].state = OPT_DEFAULT; + else + opts[6].state = OPT_UNSET; opt_len = strlen(c->hostname); if (opt_len > 0) { opts[12].slen = opt_len; + opts[12].state = OPT_DEFAULT; memcpy(opts[12].s, &c->hostname, opt_len); } @@ -463,6 +480,7 @@ int dhcp(const struct ctx *c, struct iov_tail *data) encode_domain_name((char *)opts[81].s + 3, c->fqdn); opts[81].slen = opt_len; + opts[81].state = OPT_DEFAULT; } else { debug("DHCP: client FQDN option doesn't fit, skipping"); } -- 2.55.0

Anshu Kumari

3:44 p.m.

New subject: [PATCH v6 3/6] dhcp: Add option overload

When the options field is full, overflow remaining DHCP options into the sname and file fields per RFC 2132 option 52. Per RFC 2132, Section 9.5, the boot file name is always placed in the 'file' header field. When a boot file is set, the file field is reserved from overload and overflow uses only the sname field. Link: https://bugs.passt.top/show_bug.cgi?id=192 Signed-off-by: Anshu Kumari --- v6: - Changed fill_one() return type from bool to void. - Replaced per-call-site debug messages with a single reporting loop at end of fill(). - Added explicit numeric values to enum dhcp_overload. - Removed temporary buffer for boot file copy, copy directly into reply.file. - Fixed mixed code and declarations. - Fixed indentation and whitespace issues. - Added curly brackets for multi-line if clauses v5: - enhanced enum dhcp_overload to follow kernel-doc. - Inline fill_overflow() into fill() - Use state-based checks instead of slen v4: - Converted overload #defines to enum dhcp_overload. - Fixed missing whitespace in comment before */. - Boot file name always placed in 'file' header field per RFC 2132, Section 9.5; file field reserved from overload when bootfile is set; option 67 suppressed from options area. v3: - Added RFC 2132 Section 9.3 reference comment on overload constants. - Use ARRAY_SIZE(opts) instead of raw 255 in fill_overflow(). - Swapped overflow order: try sname (64 bytes) first, then file (128 bytes) — better packing and keeps file field available for boot file name. - Removed '&' from &reply.file. - Removed '+1' from memcpy — reply.file already zeroed. - opt_set_dns_search() max_len: OPT_MAX - 3 instead of sizeof(m->o). v2: - Added #define DHCP_OVERLOAD_FILE and #define DHCP_OVERLOAD_SNAME constants - Added comment documenting space reservation: /* Reserve 3 bytes for option 52 */ - Fixed DNS search length: sizeof(m->o) only, not combined with file+sname - Removed dhcp_boot references — reply.file copy now reads from opts[67] - Used DHCP_OVERLOAD_FILE constant in reply.file guard --- dhcp.c | 98 ++++++++++++++++++++++++++++++++++++++++++++++++---------- 1 file changed, 81 insertions(+), 17 deletions(-) diff --git a/dhcp.c b/dhcp.c index 321968a..02c7744 100644 --- a/dhcp.c +++ b/dhcp.c @@ -146,16 +146,14 @@ struct msg { * @size: Usable size of @buf (excluding end marker) * @o: Option number * @offset: Current offset within @buf, updated on insertion - * - * Return: false if @buf has space to write the option, true otherwise */ -static bool fill_one(uint8_t *buf, size_t size, int o, int *offset) +static void fill_one(uint8_t *buf, size_t size, int o, int *offset) { size_t slen = opts[o].slen; /* If we don't have space to write the option, then just skip */ if (*offset + 2 /* code and length of option */ + slen > size) - return true; + return; buf[*offset] = o; buf[*offset + 1] = slen; @@ -167,19 +165,37 @@ static bool fill_one(uint8_t *buf, size_t size, int o, int *offset) opts[o].sent = 1; *offset += slen; - return false; } /** - * fill() - Fill options in message - * @m: Message to fill + * enum dhcp_overload - DHCP option overload values (RFC 2132, Section 9.3) + * @DHCP_OVERLOAD_NONE: No overload + * @DHCP_OVERLOAD_FILE: file field carries options + * @DHCP_OVERLOAD_SNAME: sname field carries options + */ +enum dhcp_overload { + DHCP_OVERLOAD_NONE = 0, + DHCP_OVERLOAD_FILE = 1, + DHCP_OVERLOAD_SNAME = 2, +}; + +/** + * fill() - Fill options in message, with overload into file/sname if needed + * @m: Message to fill + * @overload: Set to option 52 value (0 if none, 1/2/3 per RFC 2132) + * @has_bootfile: Reserve file field for boot file name * * Return: current size of options field */ -static int fill(struct msg *m) +static int fill(struct msg *m, enum dhcp_overload *overload, bool has_bootfile) { + int sname_off = 0, file_off = 0; + /* Reserve 3 bytes for option 52 (overload) if needed */ + size_t size = OPT_MAX - 3; int i, o, offset = 0; + *overload = DHCP_OVERLOAD_NONE; + for (o = 0; o < 255; o++) opts[o].sent = 0; @@ -188,20 +204,54 @@ static int fill(struct msg *m) * Put it there explicitly, unless requested via option 55. */ if (opts[55].clen > 0 && !memchr(opts[55].c, 53, opts[55].clen)) - if (fill_one(m->o, OPT_MAX, 53, &offset)) - debug("DHCP: skipping option 53"); + fill_one(m->o, size, 53, &offset); for (i = 0; i < opts[55].clen; i++) { o = opts[55].c[i]; if (opts[o].state != OPT_UNSET) - if (fill_one(m->o, OPT_MAX, o, &offset)) - debug("DHCP: skipping option %i", o); + fill_one(m->o, size, o, &offset); } for (o = 0; o < 255; o++) { if (opts[o].state != OPT_UNSET && !opts[o].sent) - if (fill_one(m->o, OPT_MAX, o, &offset)) - debug("DHCP: skipping option %i", o); + fill_one(m->o, size, o, &offset); + } + + /* Overflow unsent options into sname, then file */ + for (o = 0; (size_t)o < ARRAY_SIZE(opts); o++) { + if (opts[o].state == OPT_UNSET || opts[o].sent) + continue; + fill_one(m->sname, sizeof(m->sname) - 1, o, &sname_off); + } + + if (!has_bootfile) { + for (o = 0; (size_t)o < ARRAY_SIZE(opts); o++) { + if (opts[o].state == OPT_UNSET || opts[o].sent) + continue; + fill_one(m->file, sizeof(m->file) - 1, o, &file_off); + } + } + + /* Report any options that could not be sent */ + for (o = 0; (size_t)o < ARRAY_SIZE(opts); o++) { + if (opts[o].state != OPT_UNSET && !opts[o].sent) + debug("DHCP: skipping option %i", o); + } + + if (sname_off) { + m->sname[sname_off] = 255; + *overload |= DHCP_OVERLOAD_SNAME; + } + + if (file_off) { + m->file[file_off] = 255; + *overload |= DHCP_OVERLOAD_FILE; + } + + if (*overload) { + m->o[offset++] = 52; + m->o[offset++] = 1; + m->o[offset++] = *overload; } m->o[offset++] = 255; @@ -315,6 +365,7 @@ static void opt_set_dns_search(const struct ctx *c, size_t max_len) int dhcp(const struct ctx *c, struct iov_tail *data) { char macstr[ETH_ADDRSTRLEN]; + enum dhcp_overload overload; size_t mlen, dlen, opt_len; struct in_addr mask, dst; struct ethhdr eh_storage; @@ -325,6 +376,7 @@ int dhcp(const struct ctx *c, struct iov_tail *data) const struct udphdr *uh; struct msg m_storage; struct msg const *m; + bool has_bootfile; struct msg reply; unsigned int i; @@ -486,10 +538,22 @@ int dhcp(const struct ctx *c, struct iov_tail *data) } } - if (!c->no_dhcp_dns_search) - opt_set_dns_search(c, sizeof(m->o)); + if (!c->no_dhcp_dns_search) { + /* 3 bytes reserved for option 52 (code, length, value) */ + opt_set_dns_search(c, OPT_MAX - 3); + } + + /* RFC 2132, Section 9.5: put boot file name in the 'file' header + * field. Suppress option 67 from the options area and reserve + * the file field from overload. + */ + has_bootfile = opts[67].slen > 0 && + (size_t)opts[67].slen < sizeof(reply.file); + + dlen = offsetof(struct msg, o) + fill(&reply, &overload, has_bootfile); - dlen = offsetof(struct msg, o) + fill(&reply); + if (has_bootfile) + memcpy(reply.file, opts[67].s, opts[67].slen); if (m->flags & FLAG_BROADCAST) dst = in4addr_broadcast; -- 2.55.0

Anshu Kumari

3:44 p.m.

New subject: [PATCH v6 4/6] dhcp: Add --dhcp-opt with option table and value parser

Introduce the --dhcp-opt flag that allows setting arbitrary DHCP options from command-line in the form [--dhcp-opt CODE,VALUE]. Add a type lookup table mapping option codes to RFC 2132 value types (IPv4, IPv4 list, integer, string) and dhcp_opt_parse() to convert CLI strings to binary wire format. Parsed options are stored in struct opts[] and injected into DHCP replies. If the same option code is given more than once, the last value wins. Link: https://bugs.passt.top/show_bug.cgi?id=192 Signed-off-by: Anshu Kumari --- v6: - dropped option 53. - Used parse_unsigned(), parse_literal(), parse_ipv4() from parse.c instead of manual strtoul/inet_pton. - Moved option-parsing variables into case 34 block scope. - Used htons()/htonl() for integer encoding. - Used assert() for boundary checks in dhcp_opt_to_str(). - Used snprintf() with %.*s for string formatting in dhcp_opt_to_str(). - Used sizeof(struct in_addr) instead of literal 4. - dhcp_opt_to_str() checks OPT_UNSET for all states, not just OPT_USER. - Added curly brackets for multi-line conditionals. - Dropped trailing comma after OPT_DEFAULT in initializers to reduce line length. v5: - Rename enum values: INT8/INT16/INT32/SINT32 → UINT8/UINT16/UINT32/INT32 - Change int len to size_t len in dhcp_opt_parse(), remove int casts - Make dhcp_opt_parse() static, add dhcp_set_opt() to store options directly in opts[] at startup instead of double-parsing via ctx->dhcp_opts - Add OPT_USER to enum opt_state to protect user options from being overwritten by built-in defaults - Add dhcp_opt_to_str() for conf_print() display - Remove dhcp_opts[] from struct ctx in passt.h - Remove conf_dhcp_option() wrapper from conf.c v4: - Renamed custom_opts to dhcp_opts, 256 entries indexed by option code, removed MAX_CUSTOM_DHCP_OPTS and count field. - Changed str buffer from 256 to 255 bytes. - Moved function to conf.c as static conf_dhcp_option(), renamed from dhcp_add_option(). - Made dhcp_opt_parse() non-static, declared in dhcp.h - Dropped val/len from ctx struct; conf_dhcp_option() validates with temp buffer, dhcp() parses str directly into opts[] at reply time. - Replaced strtok_r() + 256-byte buffer with strcspn() + INET_ADDRSTRLEN buffer. - Added DHCP_OPT_SINT32 for option 2 (Time Offset), uses strtol() per RFC 2132 Section 8.2. - All errors in dhcp_opt_parse() return -1, removed die() calls; caller handles error message consistently. - Removed redundant !slen check in DHCP_OPT_STR case. - Omitted explicit array size for dhcp_opt_types[], arraydded bounds check before lookup. - Added errno = 0 + errno check for strtoul() in case 34. - Fixed usage text: "Set DHCP option CODE to VAL". - Improved man page: added format description and examples v3: - Replaced DHCP_OPT_INTEGER with separate DHCP_OPT_INT8/INT16/INT32 enums, removed dhcp_opt_int_width[] array. - Shared logic between DHCP_OPT_IPV4 and DHCP_OPT_IPV4_LIST — parse both as list, error if >1 in single case. - Added errno = 0 before strtoul() and check after. - Fixed range check: 1ULL << (width * 8) for all widths including width==4. - strncpy → memcpy for DHCP_OPT_STR. - Moved enum to dhcp.c since not used in other files. - Removed options 55, 61 (client-only), 119 (DNS compression, use --dhcp-search instead), 33 (IP pairs not supported). - DHCP_OPT_PARSE_BUF 1024 → char tmp[256]. - Upgraded dhcp_add_option() to call dhcp_opt_parse() and populate val[]/len. - Aligned array entries for readability. - Added tab after @DHCP_OPT_IPV4_LIST: in kerneldoc. - Reject empty value strings before parsing - Reject leading/trailing/consecutive commas in IP list values. v2: - Replaced struct lookup table + dhcp_opt_type_lookup() function with flat dhcp_opt_types[256] array indexed by code. - Consolidated DHCP_OPT_UINT8/UINT16/UINT32 into single DHCP_OPT_INTEGER with dhcp_opt_int_width[256] table. - Dropped DHCP_OPT_ROUTES / option 121 entirely. - Added kerneldoc for enum dhcp_opt_type values. - Removed curly braces from switch cases, declarations before switch. - Added newlines before return statements. - Changed IP list delimiter from space to comma (--dhcp-opt 6,1.1.1.1,8.8.8.8). - Defined DHCP_OPT_PARSE_BUF constant for bare 1024. - Added len and val[255] fields to struct here (moved from patch 1). - Added kerneldoc for @custom_opts.len and @custom_opts.val. - Wired dhcp_opt_parse() into case 32 (--dhcp-boot) to populate val/len. --- conf.c | 26 ++++- dhcp.c | 327 +++++++++++++++++++++++++++++++++++++++++++++++++++----- dhcp.h | 2 + passt.1 | 42 ++++++++ 4 files changed, 369 insertions(+), 28 deletions(-) diff --git a/conf.c b/conf.c index faf2681..e5f1108 100644 --- a/conf.c +++ b/conf.c @@ -47,6 +47,7 @@ #include "lineread.h" #include "isolation.h" #include "log.h" +#include "dhcp.h" #include "vhost_user.h" #include "epoll_ctl.h" #include "conf.h" @@ -632,7 +633,8 @@ static void usage(const char *name, FILE *f, int status) " -S, --search LIST Space-separated list, search domains\n" " a single, empty option disables the DNS search list\n" " -H, --hostname NAME Hostname to configure client with\n" - " --fqdn NAME FQDN to configure client with\n"); + " --fqdn NAME FQDN to configure client with\n" + " --dhcp-opt CODE,VAL Set DHCP option CODE to VAL\n"); if (strstr(name, "pasta")) FPRINTF(f, " default: don't use any search list\n"); else @@ -860,6 +862,9 @@ static void conf_print(const struct ctx *c) info(" router: %s", inet_ntop(AF_INET, &c->ip4.guest_gw, buf, sizeof(buf))); + for (i = 1; i < 255; i++) + if (dhcp_opt_to_str(i, buf, sizeof(buf))) + info(" option %u: %s", i, buf); } for (i = 0; i < ARRAY_SIZE(c->ip4.dns); i++) { @@ -1348,6 +1353,7 @@ void conf(struct ctx *c, int argc, char **argv) {"stats", required_argument, NULL, 31 }, {"conf-path", required_argument, NULL, 'c' }, {"chroot-fallback", no_argument, NULL, 32 }, + {"dhcp-opt", required_argument, NULL, 34 }, { 0 }, }; const char *optstring = "+dqfel:hs:c:F:I:p:P:m:a:n:M:g:i:o:D:S:H:461t:u:T:U:"; @@ -1589,6 +1595,24 @@ void conf(struct ctx *c, int argc, char **argv) case 32: c->chroot_fallback = true; break; + case 34: { + unsigned long optcode; + + p = optarg; + + if (!parse_unsigned(&p, 0, &optcode) || + !parse_literal(&p, ",")) { + die("--dhcp-opt requires CODE,VALUE format"); + } + + if (optcode < 1 || optcode > 254) { + die("DHCP option code must be 1-254: %s", + optarg); + } + + dhcp_set_opt(optcode, p); + break; + } case 'd': c->debug = 1; c->quiet = 0; diff --git a/dhcp.c b/dhcp.c index 02c7744..43ce133 100644 --- a/dhcp.c +++ b/dhcp.c @@ -23,6 +23,7 @@ #include #include #include +#include #include "util.h" #include "ip.h" @@ -32,15 +33,18 @@ #include "tap.h" #include "log.h" #include "dhcp.h" +#include "parse.h" /** * enum opt_state - DHCP option state * @OPT_UNSET: Option not configured * @OPT_DEFAULT: Option derived from host configuration + * @OPT_USER: Option set via --dhcp-opt command line */ enum opt_state { OPT_UNSET = 0, OPT_DEFAULT, + OPT_USER, }; /** @@ -50,7 +54,7 @@ enum opt_state { * @s: Option payload from server * @clen: Length of option received from client, -1 if not received * @c: Option payload from client - * @state: Option state (unset or default) + * @state: Option state (unset, default, or user) */ struct opt { int sent; @@ -85,17 +89,24 @@ static struct opt opts[256]; */ void dhcp_init(void) { - /* Mask */ - opts[1] = (struct opt) { 0, 4, { 0 }, 0, { 0 }, OPT_DEFAULT, }; - /* Router */ - opts[3] = (struct opt) { 0, 4, { 0 }, 0, { 0 }, OPT_DEFAULT, }; - /* Lease time */ - opts[51] = (struct opt) { 0, 4, { 0xff, 0xff, 0xff, 0xff }, - 0, { 0 }, OPT_DEFAULT }; + int i; + + for (i = 0; i < ARRAY_SIZE(opts); i++) + if (opts[i].state != OPT_USER) + opts[i].state = OPT_UNSET; + + if (opts[1].state != OPT_USER) /* Mask */ + opts[1] = (struct opt) { 0, 4, { 0 }, 0, { 0 }, OPT_DEFAULT }; + if (opts[3].state != OPT_USER) /* Router */ + opts[3] = (struct opt) { 0, 4, { 0 }, 0, { 0 }, OPT_DEFAULT }; + if (opts[51].state != OPT_USER) /* Lease time */ + opts[51] = (struct opt) { 0, 4, { 0xff, 0xff, 0xff, 0xff }, + 0, { 0 }, OPT_DEFAULT }; /* Type */ - opts[53] = (struct opt) { 0, 1, { 0 }, 0, { 0 }, OPT_DEFAULT, }; - /* Server ID */ - opts[54] = (struct opt) { 0, 4, { 0 }, 0, { 0 }, OPT_DEFAULT, }; + opts[53] = (struct opt) { 0, 1, { 0 }, 0, { 0 }, OPT_DEFAULT }; + if (opts[54].state != OPT_USER) /* Server ID */ + opts[54] = (struct opt) { 0, 4, { 0 }, 0, { 0 }, + OPT_DEFAULT }; } /** @@ -140,6 +151,258 @@ struct msg { uint8_t o[OPT_MAX + 1 /* End option */ ]; } __attribute__((__packed__)); +/** + * enum dhcp_opt_type - DHCP option value types per RFC 2132 + * @DHCP_OPT_NONE: Unsupported or unknown option + * @DHCP_OPT_STR: Variable-length string + * @DHCP_OPT_IPV4: Single IPv4 address + * @DHCP_OPT_IPV4_LIST: Multiple IPv4 addresses, comma-separated + * @DHCP_OPT_UINT8: Unsigned 8-bit integer + * @DHCP_OPT_UINT16: Unsigned 16-bit integer + * @DHCP_OPT_UINT32: Unsigned 32-bit integer + * @DHCP_OPT_INT32: Signed 32-bit integer + */ +enum dhcp_opt_type { + DHCP_OPT_NONE, + DHCP_OPT_STR, + DHCP_OPT_IPV4, + DHCP_OPT_IPV4_LIST, + DHCP_OPT_UINT8, + DHCP_OPT_UINT16, + DHCP_OPT_UINT32, + DHCP_OPT_INT32, +}; + +/** + * dhcp_opt_types - Maps option code to RFC 2132 value type, indexed by code + */ +static const enum dhcp_opt_type dhcp_opt_types[] = { + [1] = DHCP_OPT_IPV4, /* Subnet Mask */ + [2] = DHCP_OPT_INT32, /* Time Offset */ + [3] = DHCP_OPT_IPV4_LIST, /* Router */ + [4] = DHCP_OPT_IPV4_LIST, /* Time Server */ + [5] = DHCP_OPT_IPV4_LIST, /* Name Server */ + [6] = DHCP_OPT_IPV4_LIST, /* Domain Name Server */ + [7] = DHCP_OPT_IPV4_LIST, /* Log Server */ + [8] = DHCP_OPT_IPV4_LIST, /* Cookie Server */ + [9] = DHCP_OPT_IPV4_LIST, /* LPR Server */ + [10] = DHCP_OPT_IPV4_LIST, /* Impress Server */ + [11] = DHCP_OPT_IPV4_LIST, /* Resource Location Server */ + [12] = DHCP_OPT_STR, /* Host Name */ + [13] = DHCP_OPT_UINT16, /* Boot File Size */ + [15] = DHCP_OPT_STR, /* Domain Name */ + [16] = DHCP_OPT_IPV4, /* Swap Server */ + [17] = DHCP_OPT_STR, /* Root Path */ + [19] = DHCP_OPT_UINT8, /* IP Forwarding */ + [23] = DHCP_OPT_UINT8, /* Default IP TTL */ + [26] = DHCP_OPT_UINT16, /* Interface MTU */ + [28] = DHCP_OPT_IPV4, /* Broadcast Address */ + [37] = DHCP_OPT_UINT8, /* TCP Default TTL */ + [38] = DHCP_OPT_UINT32, /* TCP Keepalive Interval */ + [40] = DHCP_OPT_STR, /* NIS Domain Name */ + [41] = DHCP_OPT_IPV4_LIST, /* NIS Servers */ + [42] = DHCP_OPT_IPV4_LIST, /* NTP Servers */ + [44] = DHCP_OPT_IPV4_LIST, /* NetBIOS Name Server */ + [50] = DHCP_OPT_IPV4, /* Requested IP Address */ + [51] = DHCP_OPT_UINT32, /* IP Address Lease Time */ + [54] = DHCP_OPT_IPV4, /* Server Identifier */ + [57] = DHCP_OPT_UINT16, /* Max DHCP Message Size */ + [58] = DHCP_OPT_UINT32, /* Renewal (T1) Time */ + [59] = DHCP_OPT_UINT32, /* Rebinding (T2) Time */ + [60] = DHCP_OPT_STR, /* Vendor Class Identifier */ + [66] = DHCP_OPT_STR, /* TFTP Server Name */ + [67] = DHCP_OPT_STR, /* Bootfile Name */ + [252] = DHCP_OPT_STR, /* WPAD URL */ +}; + +/** + * dhcp_opt_parse() - Parse a DHCP option value + * @code: DHCP option code + * @str: Value string from command line + * @buf: Output buffer for binary value + * @buf_len: Size of output buffer + * + * Return: number of bytes written to @buf, or -1 on error + */ +static int dhcp_opt_parse(uint8_t code, const char *str, + uint8_t *buf, size_t buf_len) +{ + enum dhcp_opt_type type; + unsigned long val; + uint8_t width; + size_t slen; + size_t len; + char *end; + + if (code >= ARRAY_SIZE(dhcp_opt_types)) + return -1; + + type = dhcp_opt_types[code]; + + if (!*str) + return -1; + + switch (type) { + case DHCP_OPT_NONE: + return -1; + case DHCP_OPT_IPV4: + case DHCP_OPT_IPV4_LIST: + len = 0; + + do { + if (len + sizeof(struct in_addr) > buf_len) + return -1; + + if (!parse_ipv4(&str, + (struct in_addr *)(buf + len))) + return -1; + + len += sizeof(struct in_addr); + + if (type == DHCP_OPT_IPV4) + break; + } while (parse_literal(&str, ",")); + + if (!len || !parse_eoi(str)) + return -1; + + return len; + case DHCP_OPT_UINT8: + case DHCP_OPT_UINT16: + case DHCP_OPT_UINT32: + case DHCP_OPT_INT32: + if (type == DHCP_OPT_UINT8) + width = 1; + else if (type == DHCP_OPT_UINT16) + width = 2; + else + width = 4; + + if (buf_len < width) + return -1; + + errno = 0; + if (type == DHCP_OPT_INT32) { + long sval; + + sval = strtol(str, &end, 0); + if (*end || errno || + sval < INT32_MIN || sval > INT32_MAX) + return -1; + val = (uint32_t)sval; + } else { + val = strtoul(str, &end, 0); + if (*end || errno || + val >= (1ULL << (width * 8))) + return -1; + } + + if (type == DHCP_OPT_UINT16) + *(uint16_t *)buf = htons(val); + else if (type == DHCP_OPT_UINT32 || + type == DHCP_OPT_INT32) + *(uint32_t *)buf = htonl(val); + else + buf[0] = val; + + return width; + case DHCP_OPT_STR: + slen = strlen(str); + + if (slen >= buf_len) + return -1; + + memcpy(buf, str, slen); + + return slen; + } + + return -1; +} + +/** + * dhcp_set_opt() - Parse and store a user-specified DHCP option + * @code: DHCP option code + * @val_str: Value string from command line + */ +void dhcp_set_opt(uint8_t code, const char *val_str) +{ + int ret; + + ret = dhcp_opt_parse(code, val_str, opts[code].s, sizeof(opts[code].s)); + if (ret < 0) + die("Invalid value for DHCP option %u: %s", code, val_str); + + opts[code].slen = ret; + opts[code].state = OPT_USER; +} + +/** + * dhcp_opt_to_str() - Render a binary DHCP option value to a printable string + * @code: DHCP option code + * @buf: Output string buffer + * @buf_len: Size of output buffer + * + * Return: pointer to @buf if option is set, NULL otherwise + */ +const char *dhcp_opt_to_str(uint8_t code, char *buf, size_t buf_len) +{ + enum dhcp_opt_type type; + unsigned int i; + int off = 0; + + if (opts[code].state == OPT_UNSET) + return NULL; + + assert(code < ARRAY_SIZE(dhcp_opt_types)); + + type = dhcp_opt_types[code]; + + switch (type) { + case DHCP_OPT_IPV4: + case DHCP_OPT_IPV4_LIST: + for (i = 0; i + sizeof(struct in_addr) <= (unsigned int)opts[code].slen; + i += sizeof(struct in_addr)) { + if (off) + off += snprintf(buf + off, buf_len - off, ","); + inet_ntop(AF_INET, opts[code].s + i, + buf + off, buf_len - off); + off = strlen(buf); + } + return buf; + case DHCP_OPT_UINT8: + case DHCP_OPT_UINT16: + case DHCP_OPT_UINT32: { + unsigned val = 0; + int j; + + for (j = 0; j < opts[code].slen; j++) + val = (val << 8) | opts[code].s[j]; + + if (snprintf(buf, buf_len, "%u", val) >= (int)buf_len) + return NULL; + return buf; + } + case DHCP_OPT_INT32: { + int val = 0; + int j; + + for (j = 0; j < opts[code].slen; j++) + val = (val << 8) | opts[code].s[j]; + + if (snprintf(buf, buf_len, "%d", val) >= (int)buf_len) + return NULL; + return buf; + } + case DHCP_OPT_STR: + (void)snprintf(buf, buf_len, "%.*s", + opts[code].slen, opts[code].s); + return buf; + default: + assert(0); + } +} + /** * fill_one() - Fill a single option into a buffer * @buf: Buffer to write option @@ -474,14 +737,20 @@ int dhcp(const struct ctx *c, struct iov_tail *data) info(" from %s", eth_ntop(m->chaddr, macstr, sizeof(macstr))); mask.s_addr = htonl(0xffffffff << (32 - c->ip4.prefix_len)); - memcpy(opts[1].s, &mask, sizeof(mask)); - memcpy(opts[3].s, &c->ip4.guest_gw, sizeof(c->ip4.guest_gw)); - memcpy(opts[54].s, &c->ip4.our_tap_addr, sizeof(c->ip4.our_tap_addr)); + if (opts[1].state != OPT_USER) + memcpy(opts[1].s, &mask, sizeof(mask)); + if (opts[3].state != OPT_USER) + memcpy(opts[3].s, &c->ip4.guest_gw, sizeof(c->ip4.guest_gw)); + if (opts[54].state != OPT_USER) { + memcpy(opts[54].s, &c->ip4.our_tap_addr, + sizeof(c->ip4.our_tap_addr)); + } /* If the gateway is not on the assigned subnet, send an option 121 * (Classless Static Routing) adding a dummy route to it. */ - if ((c->ip4.addr.s_addr & mask.s_addr) + if (opts[121].state != OPT_USER && + (c->ip4.addr.s_addr & mask.s_addr) != (c->ip4.guest_gw.s_addr & mask.s_addr)) { /* a.b.c.d/32:0.0.0.0, 0:a.b.c.d */ opts[121].slen = 14; @@ -493,27 +762,31 @@ int dhcp(const struct ctx *c, struct iov_tail *data) &c->ip4.guest_gw, sizeof(c->ip4.guest_gw)); } - if (c->mtu) { + if (opts[26].state != OPT_USER && c->mtu) { opts[26].slen = 2; opts[26].state = OPT_DEFAULT; opts[26].s[0] = c->mtu / 256; opts[26].s[1] = c->mtu % 256; } - for (i = 0, opts[6].slen = 0; - !c->no_dhcp_dns && i < ARRAY_SIZE(c->ip4.dns); i++) { - if (IN4_IS_ADDR_UNSPECIFIED(&c->ip4.dns[i])) - break; - ((struct in_addr *)opts[6].s)[i] = c->ip4.dns[i]; - opts[6].slen += sizeof(uint32_t); + if (opts[6].state != OPT_USER) { + opts[6].slen = 0; + for (i = 0; + !c->no_dhcp_dns && i < ARRAY_SIZE(c->ip4.dns); + i++) { + if (IN4_IS_ADDR_UNSPECIFIED(&c->ip4.dns[i])) + break; + ((struct in_addr *)opts[6].s)[i] = c->ip4.dns[i]; + opts[6].slen += sizeof(uint32_t); + } + if (opts[6].slen) + opts[6].state = OPT_DEFAULT; + else + opts[6].state = OPT_UNSET; } - if (opts[6].slen) - opts[6].state = OPT_DEFAULT; - else - opts[6].state = OPT_UNSET; opt_len = strlen(c->hostname); - if (opt_len > 0) { + if (opts[12].state != OPT_USER && opt_len > 0) { opts[12].slen = opt_len; opts[12].state = OPT_DEFAULT; memcpy(opts[12].s, &c->hostname, opt_len); diff --git a/dhcp.h b/dhcp.h index cd50c99..80abda6 100644 --- a/dhcp.h +++ b/dhcp.h @@ -8,5 +8,7 @@ int dhcp(const struct ctx *c, struct iov_tail *data); void dhcp_init(void); +void dhcp_set_opt(uint8_t code, const char *val_str); +const char *dhcp_opt_to_str(uint8_t code, char *buf, size_t buf_len); #endif /* DHCP_H */ diff --git a/passt.1 b/passt.1 index 53e072a..b4a44c5 100644 --- a/passt.1 +++ b/passt.1 @@ -440,6 +440,48 @@ Send \fIname\fR as DHCP option 12 (hostname). FQDN to configure the client with. Send \fIname\fR as Client FQDN: DHCP option 81 and DHCPv6 option 39. +.TP +.BR \-\-dhcp-opt " " \fICODE\fR,\fIVALUE\fR +Set DHCP option \fICODE\fR (1\-254) to \fIVALUE\fR. The value format depends +on the option type and is determined automatically from the option code. +Multiple IPv4 addresses are comma-separated. +This option can be specified multiple times. If the same option code is +given more than once, the last value wins. Options set with +\fB\-\-dhcp-opt\fR override built-in values. +.PP +Examples: +.nf + \-\-dhcp-opt 6,8.8.8.8,4.4.4.4 + \-\-dhcp-opt 12,myhostname +.fi +.PP +Only the following option codes are supported (unsupported codes cause an error): +.RS +.TP +.B IPv4 address options +1 (Subnet Mask), 16 (Swap Server), 28 (Broadcast Address), 50 (Requested IP), +54 (Server Identifier) +.TP +.B IPv4 address list options (comma-separated) +3 (Router), 4 (Time Server), 5 (Name Server), 6 (DNS), 7 (Log Server), +8 (Cookie Server), 9 (LPR Server), 10 (Impress Server), +11 (Resource Location Server), 41 (NIS Servers), +42 (NTP Servers), 44 (NetBIOS Name Server) +.TP +.B Integer options +2 (Time Offset, 32-bit), 13 (Boot File Size, 16-bit), 19 (IP Forwarding, 8-bit), +23 (Default IP TTL, 8-bit), 26 (Interface MTU, 16-bit), +37 (TCP Default TTL, 8-bit), 38 (TCP Keepalive Interval, 32-bit), +51 (IP Address Lease Time, 32-bit), +57 (Max DHCP Message Size, 16-bit), +58 (Renewal Time, 32-bit), 59 (Rebinding Time, 32-bit) +.TP +.B String options +12 (Host Name), 15 (Domain Name), 17 (Root Path), 40 (NIS Domain Name), +60 (Vendor Class Identifier), 66 (TFTP Server Name), +67 (Bootfile Name), 252 (WPAD URL) +.RE + .TP .BR \-t ", " \-\-tcp-ports " " \fIspec Configure TCP port forwarding to guest or namespace. \fIspec\fR can be either: -- 2.55.0

Anshu Kumari

3:44 p.m.

New subject: [PATCH v6 5/6] dhcp: Add --dhcp-boot command-line option

Add a convenience shorthand --dhcp-boot FILE that sets the boot file name (DHCP option 67) for network boot. This is equivalent to --dhcp-opt 67,FILE. Link: https://bugs.passt.top/show_bug.cgi?id=192 Signed-off-by: Anshu Kumari --- v6: - no changes. v5: - replaced conf_dhcp_option() to dhcp_set_opt(). v4: - Changed argument name from URL to FILE in usage and man page. - Fixed UEFI HTTP boot wording in man page v3: - case 32 now calls dhcp_add_option(c, 67, optarg). - Handles duplicate codes: --dhcp-boot and --dhcp-opt 67 coexist correctly, last value wins. v2: - Removed separate dhcp_boot[PATH_MAX] field — --dhcp-boot foo now stores into custom_opts[] as code 67 (same as --dhcp-opt 67,foo) --- conf.c | 5 +++++ passt.1 | 7 +++++++ 2 files changed, 12 insertions(+) diff --git a/conf.c b/conf.c index e5f1108..04e9f6e 100644 --- a/conf.c +++ b/conf.c @@ -634,6 +634,7 @@ static void usage(const char *name, FILE *f, int status) " a single, empty option disables the DNS search list\n" " -H, --hostname NAME Hostname to configure client with\n" " --fqdn NAME FQDN to configure client with\n" + " --dhcp-boot FILE Boot file name for network boot\n" " --dhcp-opt CODE,VAL Set DHCP option CODE to VAL\n"); if (strstr(name, "pasta")) FPRINTF(f, " default: don't use any search list\n"); @@ -1353,6 +1354,7 @@ void conf(struct ctx *c, int argc, char **argv) {"stats", required_argument, NULL, 31 }, {"conf-path", required_argument, NULL, 'c' }, {"chroot-fallback", no_argument, NULL, 32 }, + {"dhcp-boot", required_argument, NULL, 33 }, {"dhcp-opt", required_argument, NULL, 34 }, { 0 }, }; @@ -1595,6 +1597,9 @@ void conf(struct ctx *c, int argc, char **argv) case 32: c->chroot_fallback = true; break; + case 33: + dhcp_set_opt(67, optarg); + break; case 34: { unsigned long optcode; diff --git a/passt.1 b/passt.1 index b4a44c5..989d92b 100644 --- a/passt.1 +++ b/passt.1 @@ -440,6 +440,13 @@ Send \fIname\fR as DHCP option 12 (hostname). FQDN to configure the client with. Send \fIname\fR as Client FQDN: DHCP option 81 and DHCPv6 option 39. +.TP +.BR \-\-dhcp-boot " " \fIfile +Convenience shorthand for \fB\-\-dhcp-opt\fR 67,\fIfile\fR. +Sets the boot file name (DHCP option 67) for network boot. +For UEFI HTTP boot, the vendor class identifier also needs to be set using +\fB\-\-dhcp-opt\fR 60,HTTPClient. + .TP .BR \-\-dhcp-opt " " \fICODE\fR,\fIVALUE\fR Set DHCP option \fICODE\fR (1\-254) to \fIVALUE\fR. The value format depends -- 2.55.0

Anshu Kumari

3:44 p.m.

New subject: [PATCH v6 6/6] dhcp: Add RFC 3396 option splitting for concatenation-requiring options

Implement option splitting per RFC 3396 for options that may exceed 255 bytes. A new concat_req[] lookup table marks options requiring concatenation (currently option 81, Client FQDN per RFC 4702). The opts[].s buffer is resized from 255 to 497 bytes (OPT_CONCAT_MAX) to hold the maximum data that can be split across the options field, file field, and sname field. When a concatenation-requiring option does not fit as a single option in any field, fill() calls fill_split() to split it across fields in RFC 3396 order: options field first, then file, then sname. Link: https://bugs.passt.top/show_bug.cgi?id=192 Signed-off-by: Anshu Kumari --- v6: - Merged v5 patches 6/7 and 7/7 into a single patch. - Replaced DHCP_OPT_STR_CONCAT enum value and is_concat_opt() helper with a concat_req[] boolean lookup table. - Used MIN() macro instead of ternary for chunk size. - Fixed space calculation to account for 2-byte code+length overhead per chunk. v5: - New patch: implement option splitting per RFC 3396 for options exceeding 255 bytes - Add DHCP_OPT_STR_CONCAT type, is_concat_opt(), fill_split() helpers - Resize opts[].s from 255 to OPT_CONCAT_MAX (497) bytes - Add /* fallthrough */ between DHCP_OPT_STR and DHCP_OPT_STR_CONCAT case --- dhcp.c | 99 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 98 insertions(+), 1 deletion(-) diff --git a/dhcp.c b/dhcp.c index 43ce133..eda04d1 100644 --- a/dhcp.c +++ b/dhcp.c @@ -35,6 +35,11 @@ #include "dhcp.h" #include "parse.h" +/* RFC 3396: maximum option data that can be split across options field, + * file field, and sname field (minus code+length overhead per portion). + */ +#define OPT_CONCAT_MAX 497 + /** * enum opt_state - DHCP option state * @OPT_UNSET: Option not configured @@ -59,7 +64,7 @@ enum opt_state { struct opt { int sent; int slen; - uint8_t s[255]; + uint8_t s[OPT_CONCAT_MAX]; int clen; uint8_t c[255]; enum opt_state state; @@ -215,6 +220,13 @@ static const enum dhcp_opt_type dhcp_opt_types[] = { [252] = DHCP_OPT_STR, /* WPAD URL */ }; +/** + * concat_req - Options requiring RFC 3396 concatenation, indexed by code + */ +static const bool concat_req[256] = { + [81] = true, /* Client FQDN (RFC 4702, Section 2) */ +}; + /** * dhcp_opt_parse() - Parse a DHCP option value * @code: DHCP option code @@ -309,6 +321,9 @@ static int dhcp_opt_parse(uint8_t code, const char *str, case DHCP_OPT_STR: slen = strlen(str); + if (!concat_req[code] && slen > 255) + return -1; + if (slen >= buf_len) return -1; @@ -442,6 +457,40 @@ enum dhcp_overload { DHCP_OVERLOAD_SNAME = 2, }; +/** + * fill_split() - Write a split portion of an option into a buffer + * @buf: Buffer to write into + * @size: Usable size of @buf + * @o: Option number (code) + * @offset: Current offset within @buf, updated on write + * @data: Pointer to remaining option data to write + * @remaining: Bytes of option data still to write + * + * Return: number of data bytes written (excluding code+length header) + */ +static size_t fill_split(uint8_t *buf, size_t size, int o, int *offset, + const uint8_t *data, size_t remaining) +{ + size_t avail, chunk; + + if (*offset + 2 >= (int)size) + return 0; + + avail = size - *offset - 2; + chunk = MIN(remaining, avail); + if (!chunk) + return 0; + + buf[*offset] = o; + buf[*offset + 1] = chunk; + *offset += 2; + + memcpy(buf + *offset, data, chunk); + *offset += chunk; + + return chunk; +} + /** * fill() - Fill options in message, with overload into file/sname if needed * @m: Message to fill @@ -495,6 +544,54 @@ static int fill(struct msg *m, enum dhcp_overload *overload, bool has_bootfile) } } + /* RFC 3396: split concatenation-requiring options that didn't fit + * as a single option. Split order: options, file, sname. + */ + for (o = 0; (size_t)o < ARRAY_SIZE(opts); o++) { + size_t file_cap, sname_cap, total, written; + + if (opts[o].state == OPT_UNSET || opts[o].sent || + !concat_req[o]) + continue; + + sname_cap = sizeof(m->sname) - 1 > (size_t)sname_off ? + sizeof(m->sname) - 1 - sname_off : 0; + + if (has_bootfile || sizeof(m->file) - 1 <= (size_t)file_off) + file_cap = 0; + else + file_cap = sizeof(m->file) - 1 - file_off; + + total = (size > (size_t)offset ? size - offset - 2 : 0) + + (file_cap > 2 ? file_cap - 2 : 0) + + (sname_cap > 2 ? sname_cap - 2 : 0); + + if (total < (size_t)opts[o].slen) { + debug("DHCP: skipping option %i (no space to split)", + o); + continue; + } + + written = 0; + written += fill_split(m->o, size, o, &offset, + opts[o].s, opts[o].slen); + if (written < (size_t)opts[o].slen && !has_bootfile) + written += fill_split(m->file, + sizeof(m->file) - 1, o, + &file_off, + opts[o].s + written, + opts[o].slen - written); + if (written < (size_t)opts[o].slen) + written += fill_split(m->sname, + sizeof(m->sname) - 1, o, + &sname_off, + opts[o].s + written, + opts[o].slen - written); + + if (written >= (size_t)opts[o].slen) + opts[o].sent = 1; + } + /* Report any options that could not be sent */ for (o = 0; (size_t)o < ARRAY_SIZE(opts); o++) { if (opts[o].state != OPT_UNSET && !opts[o].sent) -- 2.55.0

Laurent Vivier

25 Aug 25 Aug

5:13 p.m.

New subject: [PATCH v6 1/6] dhcp: Refactor fill_one() to operate on a generic buffer

On 8/24/26 15:44, Anshu Kumari wrote:

...

Change fill_one() to accept a buffer pointer and capacity instead of a struct msg pointer. This is a pure refactor with no behavior change, preparing for option overload support where fill_one() will also write into the file and sname fields.

Link: https://bugs.passt.top/show_bug.cgi?id=192 Signed-off-by: Anshu Kumari --- v6: - no changes.

v5: - Restore debug messages for skipped options in fill() - Add /* code and length of option */ comment in size check - Use buf + *offset instead of &buf[*offset] for memcpy

v3: - Restored removed comments: "If we don't have space to write the option, then just skip" and "Move to option".

v2: - Renamed parameter cap → size. --- dhcp.c | 27 ++++++++++++++------------- 1 file changed, 14 insertions(+), 13 deletions(-)

Reviewed-by: Laurent Vivier

...

diff --git a/dhcp.c b/dhcp.c index c3c7422..bb72b72 100644 --- a/dhcp.c +++ b/dhcp.c @@ -131,28 +131,29 @@ struct msg { } __attribute__((__packed__));

/** - * fill_one() - Fill a single option in message - * @m: Message to fill + * fill_one() - Fill a single option into a buffer + * @buf: Buffer to write option + * @size: Usable size of @buf (excluding end marker) * @o: Option number - * @offset: Current offset within options field, updated on insertion + * @offset: Current offset within @buf, updated on insertion * - * Return: false if m has space to write the option, true otherwise + * Return: false if @buf has space to write the option, true otherwise */ -static bool fill_one(struct msg *m, int o, int *offset) +static bool fill_one(uint8_t *buf, size_t size, int o, int *offset) { size_t slen = opts[o].slen;

/* If we don't have space to write the option, then just skip */ - if (*offset + 2 /* code and length of option */ + slen > OPT_MAX) + if (*offset + 2 /* code and length of option */ + slen > size) return true;

- m->o[*offset] = o; - m->o[*offset + 1] = slen; + buf[*offset] = o; + buf[*offset + 1] = slen;

/* Move to option */ *offset += 2;

- memcpy(&m->o[*offset], opts[o].s, slen); + memcpy(buf + *offset, opts[o].s, slen);

opts[o].sent = 1; *offset += slen; @@ -177,19 +178,19 @@ static int fill(struct msg *m) * Put it there explicitly, unless requested via option 55. */ if (opts[55].clen > 0 && !memchr(opts[55].c, 53, opts[55].clen)) - if (fill_one(m, 53, &offset)) - debug("DHCP: skipping option 53"); + if (fill_one(m->o, OPT_MAX, 53, &offset)) + debug("DHCP: skipping option 53");

for (i = 0; i < opts[55].clen; i++) { o = opts[55].c[i]; if (opts[o].slen != -1) - if (fill_one(m, o, &offset)) + if (fill_one(m->o, OPT_MAX, o, &offset)) debug("DHCP: skipping option %i", o); }

for (o = 0; o < 255; o++) { if (opts[o].slen != -1 && !opts[o].sent) - if (fill_one(m, o, &offset)) + if (fill_one(m->o, OPT_MAX, o, &offset)) debug("DHCP: skipping option %i", o); }

Laurent Vivier

5:35 p.m.

New subject: [PATCH v6 2/6] dhcp: Add option state management with enum opt_state

On 8/24/26 15:44, Anshu Kumari wrote:

...

Overloading slen = -1 to mean "not set" conflates the option length with its lifecycle state, and can't express additional states such as "set by the user via command-line" which will be needed for --dhcp-opt support.

Introduce enum opt_state with OPT_UNSET (option not configured) and OPT_DEFAULT (derived from host configuration). Replace all slen = -1 / slen != -1 checks with state comparisons, and set state = OPT_DEFAULT for options initialised in dhcp_init() and at reply time in dhcp().

Link: https://bugs.passt.top/show_bug.cgi?id=192 Signed-off-by: Anshu Kumari --- v6: - Rewrote commit message to explain why slen = -1 overloading is problematic and how it motivates the enum. - Dropped explicit OPT_UNSET initialization loop inside dhcp_init(). - Realigned opts[51] initializer for consistency.

v5: - New patch: introduce enum opt_state { OPT_UNSET, OPT_DEFAULT } to replace slen = -1 for tracking option state - Replace all slen = -1 / slen != -1 checks with state = OPT_UNSET / state != OPT_UNSET - Set OPT_DEFAULT for options initialised in dhcp_init() and at reply time --- dhcp.c | 58 ++++++++++++++++++++++++++++++++++++++-------------------- 1 file changed, 38 insertions(+), 20 deletions(-)

Reviewed-by: Laurent Vivier one comment below

...

diff --git a/dhcp.c b/dhcp.c index bb72b72..321968a 100644 --- a/dhcp.c +++ b/dhcp.c @@ -33,13 +33,24 @@ #include "log.h" #include "dhcp.h"

+/** + * enum opt_state - DHCP option state + * @OPT_UNSET: Option not configured + * @OPT_DEFAULT: Option derived from host configuration + */ +enum opt_state { + OPT_UNSET = 0, + OPT_DEFAULT, +}; + /** * struct opt - DHCP option * @sent: Convenience flag, set while filling replies - * @slen: Length of option defined for server, -1 if not going to be sent + * @slen: Length of option defined for server * @s: Option payload from server * @clen: Length of option received from client, -1 if not received * @c: Option payload from client + * @state: Option state (unset or default) */ struct opt { int sent; @@ -47,6 +58,7 @@ struct opt { uint8_t s[255]; int clen; uint8_t c[255]; + enum opt_state state; };

static struct opt opts[256]; @@ -73,19 +85,17 @@ static struct opt opts[256]; */ void dhcp_init(void) { - int i; - - for (i = 0; i < ARRAY_SIZE(opts); i++) - opts[i].slen = -1; - - opts[1] = (struct opt) { 0, 4, { 0 }, 0, { 0 }, }; /* Mask */ - opts[3] = (struct opt) { 0, 4, { 0 }, 0, { 0 }, }; /* Router */ - opts[51] = (struct opt) { 0, 4, { 0xff, - 0xff, - 0xff, - 0xff }, 0, { 0 }, }; /* Lease time */ - opts[53] = (struct opt) { 0, 1, { 0 }, 0, { 0 }, }; /* Type */ - opts[54] = (struct opt) { 0, 4, { 0 }, 0, { 0 }, }; /* Server ID */ + /* Mask */ + opts[1] = (struct opt) { 0, 4, { 0 }, 0, { 0 }, OPT_DEFAULT, }; + /* Router */ + opts[3] = (struct opt) { 0, 4, { 0 }, 0, { 0 }, OPT_DEFAULT, }; + /* Lease time */ + opts[51] = (struct opt) { 0, 4, { 0xff, 0xff, 0xff, 0xff }, + 0, { 0 }, OPT_DEFAULT }; + /* Type */ + opts[53] = (struct opt) { 0, 1, { 0 }, 0, { 0 }, OPT_DEFAULT, }; + /* Server ID */ + opts[54] = (struct opt) { 0, 4, { 0 }, 0, { 0 }, OPT_DEFAULT, };

unneeded comma after OPT_DEFAULT

...

}

/** @@ -183,13 +193,13 @@ static int fill(struct msg *m)

for (i = 0; i < opts[55].clen; i++) { o = opts[55].c[i]; - if (opts[o].slen != -1) + if (opts[o].state != OPT_UNSET) if (fill_one(m->o, OPT_MAX, o, &offset)) debug("DHCP: skipping option %i", o); }

for (o = 0; o < 255; o++) { - if (opts[o].slen != -1 && !opts[o].sent) + if (opts[o].state != OPT_UNSET && !opts[o].sent) if (fill_one(m->o, OPT_MAX, o, &offset)) debug("DHCP: skipping option %i", o); } @@ -243,6 +253,7 @@ static void opt_set_dns_search(const struct ctx *c, size_t max_len) int i;

opts[119].slen = 0; + opts[119].state = OPT_DEFAULT;

for (i = 0; i < 255; i++) max_len -= opts[i].slen; @@ -291,7 +302,7 @@ static void opt_set_dns_search(const struct ctx *c, size_t max_len) }

if (!opts[119].slen) - opts[119].slen = -1; + opts[119].state = OPT_UNSET; }

/** @@ -389,7 +400,7 @@ int dhcp(const struct ctx *c, struct iov_tail *data) iov_drop_header(data, *olen); }

- opts[80].slen = -1; + opts[80].state = OPT_UNSET; if (opts[53].clen > 0 && opts[53].c[0] == DHCPDISCOVER) { if (opts[80].clen == -1) { info("DHCP: offer to discover"); @@ -398,6 +409,7 @@ int dhcp(const struct ctx *c, struct iov_tail *data) info("DHCP: ack to discover (Rapid Commit)"); opts[53].s[0] = DHCPACK; opts[80].slen = 0; + opts[80].state = OPT_DEFAULT; } } else if (opts[53].clen <= 0 || opts[53].c[0] == DHCPREQUEST) { info("%s: ack to request", /* DHCP needs a valid message type */ @@ -421,6 +433,7 @@ int dhcp(const struct ctx *c, struct iov_tail *data) != (c->ip4.guest_gw.s_addr & mask.s_addr)) { /* a.b.c.d/32:0.0.0.0, 0:a.b.c.d */ opts[121].slen = 14; + opts[121].state = OPT_DEFAULT; opts[121].s[0] = 32; memcpy(opts[121].s + 1, &c->ip4.guest_gw, sizeof(c->ip4.guest_gw)); @@ -430,6 +443,7 @@ int dhcp(const struct ctx *c, struct iov_tail *data)

if (c->mtu) { opts[26].slen = 2; + opts[26].state = OPT_DEFAULT; opts[26].s[0] = c->mtu / 256; opts[26].s[1] = c->mtu % 256; } @@ -441,12 +455,15 @@ int dhcp(const struct ctx *c, struct iov_tail *data) ((struct in_addr *)opts[6].s)[i] = c->ip4.dns[i]; opts[6].slen += sizeof(uint32_t); } - if (!opts[6].slen) - opts[6].slen = -1; + if (opts[6].slen) + opts[6].state = OPT_DEFAULT; + else + opts[6].state = OPT_UNSET;

opt_len = strlen(c->hostname); if (opt_len > 0) { opts[12].slen = opt_len; + opts[12].state = OPT_DEFAULT; memcpy(opts[12].s, &c->hostname, opt_len); }

@@ -463,6 +480,7 @@ int dhcp(const struct ctx *c, struct iov_tail *data) encode_domain_name((char *)opts[81].s + 3, c->fqdn);

opts[81].slen = opt_len; + opts[81].state = OPT_DEFAULT; } else { debug("DHCP: client FQDN option doesn't fit, skipping"); }

Laurent Vivier

26 Aug 26 Aug

9:56 a.m.

New subject: [PATCH v6 3/6] dhcp: Add option overload

On 8/24/26 15:44, Anshu Kumari wrote:

...

When the options field is full, overflow remaining DHCP options into the sname and file fields per RFC 2132 option 52.

Per RFC 2132, Section 9.5, the boot file name is always placed in the 'file' header field. When a boot file is set, the file field is reserved from overload and overflow uses only the sname field.

Link: https://bugs.passt.top/show_bug.cgi?id=192 Signed-off-by: Anshu Kumari --- v6: - Changed fill_one() return type from bool to void. - Replaced per-call-site debug messages with a single reporting loop at end of fill(). - Added explicit numeric values to enum dhcp_overload. - Removed temporary buffer for boot file copy, copy directly into reply.file. - Fixed mixed code and declarations. - Fixed indentation and whitespace issues. - Added curly brackets for multi-line if clauses

v5: - enhanced enum dhcp_overload to follow kernel-doc. - Inline fill_overflow() into fill() - Use state-based checks instead of slen

v4: - Converted overload #defines to enum dhcp_overload. - Fixed missing whitespace in comment before */. - Boot file name always placed in 'file' header field per RFC 2132, Section 9.5; file field reserved from overload when bootfile is set; option 67 suppressed from options area.

v3: - Added RFC 2132 Section 9.3 reference comment on overload constants. - Use ARRAY_SIZE(opts) instead of raw 255 in fill_overflow(). - Swapped overflow order: try sname (64 bytes) first, then file (128 bytes) — better packing and keeps file field available for boot file name. - Removed '&' from &reply.file. - Removed '+1' from memcpy — reply.file already zeroed. - opt_set_dns_search() max_len: OPT_MAX - 3 instead of sizeof(m->o).

v2: - Added #define DHCP_OVERLOAD_FILE and #define DHCP_OVERLOAD_SNAME constants - Added comment documenting space reservation: /* Reserve 3 bytes for option 52 */ - Fixed DNS search length: sizeof(m->o) only, not combined with file+sname - Removed dhcp_boot references — reply.file copy now reads from opts[67] - Used DHCP_OVERLOAD_FILE constant in reply.file guard --- dhcp.c | 98 ++++++++++++++++++++++++++++++++++++++++++++++++---------- 1 file changed, 81 insertions(+), 17 deletions(-)

diff --git a/dhcp.c b/dhcp.c index 321968a..02c7744 100644 --- a/dhcp.c +++ b/dhcp.c @@ -146,16 +146,14 @@ struct msg { * @size: Usable size of @buf (excluding end marker) * @o: Option number * @offset: Current offset within @buf, updated on insertion - * - * Return: false if @buf has space to write the option, true otherwise */ -static bool fill_one(uint8_t *buf, size_t size, int o, int *offset) +static void fill_one(uint8_t *buf, size_t size, int o, int *offset) { size_t slen = opts[o].slen;

/* If we don't have space to write the option, then just skip */ if (*offset + 2 /* code and length of option */ + slen > size) - return true; + return;

buf[*offset] = o; buf[*offset + 1] = slen; @@ -167,19 +165,37 @@ static bool fill_one(uint8_t *buf, size_t size, int o, int *offset)

opts[o].sent = 1; *offset += slen; - return false; }

changing the return type of fill_one() and removing debug information should be in a separate patch. It's hard to understand the change when we focus on the overload option... The patch can also explains that we rely now on opts[].sent to know if the option has been written in buf.

...

/** - * fill() - Fill options in message - * @m: Message to fill + * enum dhcp_overload - DHCP option overload values (RFC 2132, Section 9.3) + * @DHCP_OVERLOAD_NONE: No overload + * @DHCP_OVERLOAD_FILE: file field carries options + * @DHCP_OVERLOAD_SNAME: sname field carries options + */ +enum dhcp_overload { + DHCP_OVERLOAD_NONE = 0, + DHCP_OVERLOAD_FILE = 1, + DHCP_OVERLOAD_SNAME = 2, +}; + +/** + * fill() - Fill options in message, with overload into file/sname if needed + * @m: Message to fill + * @overload: Set to option 52 value (0 if none, 1/2/3 per RFC 2132) + * @has_bootfile: Reserve file field for boot file name * * Return: current size of options field */ -static int fill(struct msg *m) +static int fill(struct msg *m, enum dhcp_overload *overload, bool has_bootfile) { + int sname_off = 0, file_off = 0; + /* Reserve 3 bytes for option 52 (overload) if needed */ + size_t size = OPT_MAX - 3; int i, o, offset = 0;

+ *overload = DHCP_OVERLOAD_NONE;

Why overload is a parameter? it is only used inside the function and the set value is never read by the caller.

...

+ for (o = 0; o < 255; o++) opts[o].sent = 0;

@@ -188,20 +204,54 @@ static int fill(struct msg *m) * Put it there explicitly, unless requested via option 55. */ if (opts[55].clen > 0 && !memchr(opts[55].c, 53, opts[55].clen)) - if (fill_one(m->o, OPT_MAX, 53, &offset)) - debug("DHCP: skipping option 53"); + fill_one(m->o, size, 53, &offset);

for (i = 0; i < opts[55].clen; i++) { o = opts[55].c[i]; if (opts[o].state != OPT_UNSET) - if (fill_one(m->o, OPT_MAX, o, &offset)) - debug("DHCP: skipping option %i", o); + fill_one(m->o, size, o, &offset); }

for (o = 0; o < 255; o++) { if (opts[o].state != OPT_UNSET && !opts[o].sent) - if (fill_one(m->o, OPT_MAX, o, &offset)) - debug("DHCP: skipping option %i", o); + fill_one(m->o, size, o, &offset); + } + + /* Overflow unsent options into sname, then file */ + for (o = 0; (size_t)o < ARRAY_SIZE(opts); o++) { + if (opts[o].state == OPT_UNSET || opts[o].sent) + continue; + fill_one(m->sname, sizeof(m->sname) - 1, o, &sname_off); + } + + if (!has_bootfile) { + for (o = 0; (size_t)o < ARRAY_SIZE(opts); o++) { + if (opts[o].state == OPT_UNSET || opts[o].sent) + continue; + fill_one(m->file, sizeof(m->file) - 1, o, &file_off); + } + } + + /* Report any options that could not be sent */ + for (o = 0; (size_t)o < ARRAY_SIZE(opts); o++) { + if (opts[o].state != OPT_UNSET && !opts[o].sent) + debug("DHCP: skipping option %i", o); + } + + if (sname_off) { + m->sname[sname_off] = 255; + *overload |= DHCP_OVERLOAD_SNAME; + } + + if (file_off) { + m->file[file_off] = 255; + *overload |= DHCP_OVERLOAD_FILE; + } + + if (*overload) { + m->o[offset++] = 52; + m->o[offset++] = 1; + m->o[offset++] = *overload; }

m->o[offset++] = 255; @@ -315,6 +365,7 @@ static void opt_set_dns_search(const struct ctx *c, size_t max_len) int dhcp(const struct ctx *c, struct iov_tail *data) { char macstr[ETH_ADDRSTRLEN]; + enum dhcp_overload overload; size_t mlen, dlen, opt_len; struct in_addr mask, dst; struct ethhdr eh_storage; @@ -325,6 +376,7 @@ int dhcp(const struct ctx *c, struct iov_tail *data) const struct udphdr *uh; struct msg m_storage; struct msg const *m; + bool has_bootfile; struct msg reply; unsigned int i;

@@ -486,10 +538,22 @@ int dhcp(const struct ctx *c, struct iov_tail *data) } }

- if (!c->no_dhcp_dns_search) - opt_set_dns_search(c, sizeof(m->o)); + if (!c->no_dhcp_dns_search) { + /* 3 bytes reserved for option 52 (code, length, value) */ + opt_set_dns_search(c, OPT_MAX - 3); + } + + /* RFC 2132, Section 9.5: put boot file name in the 'file' header + * field. Suppress option 67 from the options area and reserve + * the file field from overload. + */ + has_bootfile = opts[67].slen > 0 && + (size_t)opts[67].slen < sizeof(reply.file); + + dlen = offsetof(struct msg, o) + fill(&reply, &overload, has_bootfile);

- dlen = offsetof(struct msg, o) + fill(&reply); + if (has_bootfile) + memcpy(reply.file, opts[67].s, opts[67].slen);

Perhaps the setting of reply.file could me merged in PATCH 5, and move this patch after PATCH 5?

...

if (m->flags & FLAG_BROADCAST) dst = in4addr_broadcast;

Laurent Vivier

10:09 a.m.

New subject: [PATCH v6 5/6] dhcp: Add --dhcp-boot command-line option

On 8/24/26 15:44, Anshu Kumari wrote:

...

Add a convenience shorthand --dhcp-boot FILE that sets the boot file name (DHCP option 67) for network boot. This is equivalent to --dhcp-opt 67,FILE.

Link: https://bugs.passt.top/show_bug.cgi?id=192 Signed-off-by: Anshu Kumari --- v6: - no changes.

v5: - replaced conf_dhcp_option() to dhcp_set_opt().

v4: - Changed argument name from URL to FILE in usage and man page. - Fixed UEFI HTTP boot wording in man page

v3: - case 32 now calls dhcp_add_option(c, 67, optarg). - Handles duplicate codes: --dhcp-boot and --dhcp-opt 67 coexist correctly, last value wins.

v2: - Removed separate dhcp_boot[PATH_MAX] field — --dhcp-boot foo now stores into custom_opts[] as code 67 (same as --dhcp-opt 67,foo) --- conf.c | 5 +++++ passt.1 | 7 +++++++ 2 files changed, 12 insertions(+)

You should move in this patch the change from PATCH 3 (and move PATCH 3 after this patch): + has_bootfile = opts[67].slen > 0 && + (size_t)opts[67].slen < sizeof(reply.file); + if (has_bootfile) + memcpy(reply.file, opts[67].s, opts[67].slen); except that: Reviewed-by: Laurent Vivier

...

diff --git a/conf.c b/conf.c index e5f1108..04e9f6e 100644 --- a/conf.c +++ b/conf.c @@ -634,6 +634,7 @@ static void usage(const char *name, FILE *f, int status) " a single, empty option disables the DNS search list\n" " -H, --hostname NAME Hostname to configure client with\n" " --fqdn NAME FQDN to configure client with\n" + " --dhcp-boot FILE Boot file name for network boot\n" " --dhcp-opt CODE,VAL Set DHCP option CODE to VAL\n"); if (strstr(name, "pasta")) FPRINTF(f, " default: don't use any search list\n"); @@ -1353,6 +1354,7 @@ void conf(struct ctx *c, int argc, char **argv) {"stats", required_argument, NULL, 31 }, {"conf-path", required_argument, NULL, 'c' }, {"chroot-fallback", no_argument, NULL, 32 }, + {"dhcp-boot", required_argument, NULL, 33 }, {"dhcp-opt", required_argument, NULL, 34 }, { 0 }, }; @@ -1595,6 +1597,9 @@ void conf(struct ctx *c, int argc, char **argv) case 32: c->chroot_fallback = true; break; + case 33: + dhcp_set_opt(67, optarg); + break; case 34: { unsigned long optcode;

diff --git a/passt.1 b/passt.1 index b4a44c5..989d92b 100644 --- a/passt.1 +++ b/passt.1 @@ -440,6 +440,13 @@ Send \fIname\fR as DHCP option 12 (hostname). FQDN to configure the client with. Send \fIname\fR as Client FQDN: DHCP option 81 and DHCPv6 option 39.

+.TP +.BR \-\-dhcp-boot " " \fIfile +Convenience shorthand for \fB\-\-dhcp-opt\fR 67,\fIfile\fR. +Sets the boot file name (DHCP option 67) for network boot. +For UEFI HTTP boot, the vendor class identifier also needs to be set using +\fB\-\-dhcp-opt\fR 60,HTTPClient. + .TP .BR \-\-dhcp-opt " " \fICODE\fR,\fIVALUE\fR Set DHCP option \fICODE\fR (1\-254) to \fIVALUE\fR. The value format depends

Laurent Vivier

noon

New subject: [PATCH v6 4/6] dhcp: Add --dhcp-opt with option table and value parser

On 8/24/26 15:44, Anshu Kumari wrote:

...

Introduce the --dhcp-opt flag that allows setting arbitrary DHCP options from command-line in the form [--dhcp-opt CODE,VALUE].

Add a type lookup table mapping option codes to RFC 2132 value types (IPv4, IPv4 list, integer, string) and dhcp_opt_parse() to convert CLI strings to binary wire format. Parsed options are stored in struct opts[] and injected into DHCP replies. If the same option code is given more than once, the last value wins.

Link: https://bugs.passt.top/show_bug.cgi?id=192 Signed-off-by: Anshu Kumari --- v6: - dropped option 53. - Used parse_unsigned(), parse_literal(), parse_ipv4() from parse.c instead of manual strtoul/inet_pton. - Moved option-parsing variables into case 34 block scope. - Used htons()/htonl() for integer encoding. - Used assert() for boundary checks in dhcp_opt_to_str(). - Used snprintf() with %.*s for string formatting in dhcp_opt_to_str(). - Used sizeof(struct in_addr) instead of literal 4. - dhcp_opt_to_str() checks OPT_UNSET for all states, not just OPT_USER. - Added curly brackets for multi-line conditionals. - Dropped trailing comma after OPT_DEFAULT in initializers to reduce line length.

v5: - Rename enum values: INT8/INT16/INT32/SINT32 → UINT8/UINT16/UINT32/INT32 - Change int len to size_t len in dhcp_opt_parse(), remove int casts - Make dhcp_opt_parse() static, add dhcp_set_opt() to store options directly in opts[] at startup instead of double-parsing via ctx->dhcp_opts - Add OPT_USER to enum opt_state to protect user options from being overwritten by built-in defaults - Add dhcp_opt_to_str() for conf_print() display - Remove dhcp_opts[] from struct ctx in passt.h - Remove conf_dhcp_option() wrapper from conf.c

v4: - Renamed custom_opts to dhcp_opts, 256 entries indexed by option code, removed MAX_CUSTOM_DHCP_OPTS and count field. - Changed str buffer from 256 to 255 bytes. - Moved function to conf.c as static conf_dhcp_option(), renamed from dhcp_add_option(). - Made dhcp_opt_parse() non-static, declared in dhcp.h - Dropped val/len from ctx struct; conf_dhcp_option() validates with temp buffer, dhcp() parses str directly into opts[] at reply time. - Replaced strtok_r() + 256-byte buffer with strcspn() + INET_ADDRSTRLEN buffer. - Added DHCP_OPT_SINT32 for option 2 (Time Offset), uses strtol() per RFC 2132 Section 8.2. - All errors in dhcp_opt_parse() return -1, removed die() calls; caller handles error message consistently. - Removed redundant !slen check in DHCP_OPT_STR case. - Omitted explicit array size for dhcp_opt_types[], arraydded bounds check before lookup. - Added errno = 0 + errno check for strtoul() in case 34. - Fixed usage text: "Set DHCP option CODE to VAL". - Improved man page: added format description and examples

v3: - Replaced DHCP_OPT_INTEGER with separate DHCP_OPT_INT8/INT16/INT32 enums, removed dhcp_opt_int_width[] array. - Shared logic between DHCP_OPT_IPV4 and DHCP_OPT_IPV4_LIST — parse both as list, error if >1 in single case. - Added errno = 0 before strtoul() and check after. - Fixed range check: 1ULL << (width * 8) for all widths including width==4. - strncpy → memcpy for DHCP_OPT_STR. - Moved enum to dhcp.c since not used in other files. - Removed options 55, 61 (client-only), 119 (DNS compression, use --dhcp-search instead), 33 (IP pairs not supported). - DHCP_OPT_PARSE_BUF 1024 → char tmp[256]. - Upgraded dhcp_add_option() to call dhcp_opt_parse() and populate val[]/len. - Aligned array entries for readability. - Added tab after @DHCP_OPT_IPV4_LIST: in kerneldoc. - Reject empty value strings before parsing - Reject leading/trailing/consecutive commas in IP list values.

v2: - Replaced struct lookup table + dhcp_opt_type_lookup() function with flat dhcp_opt_types[256] array indexed by code. - Consolidated DHCP_OPT_UINT8/UINT16/UINT32 into single DHCP_OPT_INTEGER with dhcp_opt_int_width[256] table. - Dropped DHCP_OPT_ROUTES / option 121 entirely. - Added kerneldoc for enum dhcp_opt_type values. - Removed curly braces from switch cases, declarations before switch. - Added newlines before return statements. - Changed IP list delimiter from space to comma (--dhcp-opt 6,1.1.1.1,8.8.8.8). - Defined DHCP_OPT_PARSE_BUF constant for bare 1024. - Added len and val[255] fields to struct here (moved from patch 1). - Added kerneldoc for @custom_opts.len and @custom_opts.val. - Wired dhcp_opt_parse() into case 32 (--dhcp-boot) to populate val/len. --- conf.c | 26 ++++- dhcp.c | 327 +++++++++++++++++++++++++++++++++++++++++++++++++++----- dhcp.h | 2 + passt.1 | 42 ++++++++ 4 files changed, 369 insertions(+), 28 deletions(-)

diff --git a/conf.c b/conf.c index faf2681..e5f1108 100644 --- a/conf.c +++ b/conf.c @@ -47,6 +47,7 @@ #include "lineread.h" #include "isolation.h" #include "log.h" +#include "dhcp.h" #include "vhost_user.h" #include "epoll_ctl.h" #include "conf.h" @@ -632,7 +633,8 @@ static void usage(const char *name, FILE *f, int status) " -S, --search LIST Space-separated list, search domains\n" " a single, empty option disables the DNS search list\n" " -H, --hostname NAME Hostname to configure client with\n" - " --fqdn NAME FQDN to configure client with\n"); + " --fqdn NAME FQDN to configure client with\n" + " --dhcp-opt CODE,VAL Set DHCP option CODE to VAL\n"); if (strstr(name, "pasta")) FPRINTF(f, " default: don't use any search list\n"); else @@ -860,6 +862,9 @@ static void conf_print(const struct ctx *c) info(" router: %s", inet_ntop(AF_INET, &c->ip4.guest_gw, buf, sizeof(buf))); + for (i = 1; i < 255; i++) + if (dhcp_opt_to_str(i, buf, sizeof(buf))) + info(" option %u: %s", i, buf); }

for (i = 0; i < ARRAY_SIZE(c->ip4.dns); i++) { @@ -1348,6 +1353,7 @@ void conf(struct ctx *c, int argc, char **argv) {"stats", required_argument, NULL, 31 }, {"conf-path", required_argument, NULL, 'c' }, {"chroot-fallback", no_argument, NULL, 32 }, + {"dhcp-opt", required_argument, NULL, 34 }, { 0 }, }; const char *optstring = "+dqfel:hs:c:F:I:p:P:m:a:n:M:g:i:o:D:S:H:461t:u:T:U:"; @@ -1589,6 +1595,24 @@ void conf(struct ctx *c, int argc, char **argv) case 32: c->chroot_fallback = true; break; + case 34: { + unsigned long optcode; + + p = optarg; + + if (!parse_unsigned(&p, 0, &optcode) || + !parse_literal(&p, ",")) { + die("--dhcp-opt requires CODE,VALUE format"); + } + + if (optcode < 1 || optcode > 254) { + die("DHCP option code must be 1-254: %s", + optarg); + } + + dhcp_set_opt(optcode, p); + break; + } case 'd': c->debug = 1; c->quiet = 0; diff --git a/dhcp.c b/dhcp.c index 02c7744..43ce133 100644 --- a/dhcp.c +++ b/dhcp.c @@ -23,6 +23,7 @@ #include #include #include +#include

#include "util.h" #include "ip.h" @@ -32,15 +33,18 @@ #include "tap.h" #include "log.h" #include "dhcp.h" +#include "parse.h"

/** * enum opt_state - DHCP option state * @OPT_UNSET: Option not configured * @OPT_DEFAULT: Option derived from host configuration + * @OPT_USER: Option set via --dhcp-opt command line */ enum opt_state { OPT_UNSET = 0, OPT_DEFAULT, + OPT_USER, };

/** @@ -50,7 +54,7 @@ enum opt_state { * @s: Option payload from server * @clen: Length of option received from client, -1 if not received * @c: Option payload from client - * @state: Option state (unset or default) + * @state: Option state (unset, default, or user) */ struct opt { int sent; @@ -85,17 +89,24 @@ static struct opt opts[256]; */ void dhcp_init(void) { - /* Mask */ - opts[1] = (struct opt) { 0, 4, { 0 }, 0, { 0 }, OPT_DEFAULT, }; - /* Router */ - opts[3] = (struct opt) { 0, 4, { 0 }, 0, { 0 }, OPT_DEFAULT, }; - /* Lease time */ - opts[51] = (struct opt) { 0, 4, { 0xff, 0xff, 0xff, 0xff }, - 0, { 0 }, OPT_DEFAULT }; + int i; + + for (i = 0; i < ARRAY_SIZE(opts); i++) + if (opts[i].state != OPT_USER) + opts[i].state = OPT_UNSET;

This is dead code as state will be set by default to 0 (OPT_UNSET)

...

+ + if (opts[1].state != OPT_USER) /* Mask */ + opts[1] = (struct opt) { 0, 4, { 0 }, 0, { 0 }, OPT_DEFAULT }; + if (opts[3].state != OPT_USER) /* Router */ + opts[3] = (struct opt) { 0, 4, { 0 }, 0, { 0 }, OPT_DEFAULT }; + if (opts[51].state != OPT_USER) /* Lease time */ + opts[51] = (struct opt) { 0, 4, { 0xff, 0xff, 0xff, 0xff }, + 0, { 0 }, OPT_DEFAULT }; /* Type */ - opts[53] = (struct opt) { 0, 1, { 0 }, 0, { 0 }, OPT_DEFAULT, }; - /* Server ID */ - opts[54] = (struct opt) { 0, 4, { 0 }, 0, { 0 }, OPT_DEFAULT, }; + opts[53] = (struct opt) { 0, 1, { 0 }, 0, { 0 }, OPT_DEFAULT }; + if (opts[54].state != OPT_USER) /* Server ID */ + opts[54] = (struct opt) { 0, 4, { 0 }, 0, { 0 }, + OPT_DEFAULT }; }

/** @@ -140,6 +151,258 @@ struct msg { uint8_t o[OPT_MAX + 1 /* End option */ ]; } __attribute__((__packed__));

+/** + * enum dhcp_opt_type - DHCP option value types per RFC 2132 + * @DHCP_OPT_NONE: Unsupported or unknown option + * @DHCP_OPT_STR: Variable-length string + * @DHCP_OPT_IPV4: Single IPv4 address + * @DHCP_OPT_IPV4_LIST: Multiple IPv4 addresses, comma-separated + * @DHCP_OPT_UINT8: Unsigned 8-bit integer + * @DHCP_OPT_UINT16: Unsigned 16-bit integer + * @DHCP_OPT_UINT32: Unsigned 32-bit integer + * @DHCP_OPT_INT32: Signed 32-bit integer + */ +enum dhcp_opt_type { + DHCP_OPT_NONE, + DHCP_OPT_STR, + DHCP_OPT_IPV4, + DHCP_OPT_IPV4_LIST, + DHCP_OPT_UINT8, + DHCP_OPT_UINT16, + DHCP_OPT_UINT32, + DHCP_OPT_INT32, +}; + +/** + * dhcp_opt_types - Maps option code to RFC 2132 value type, indexed by code + */ +static const enum dhcp_opt_type dhcp_opt_types[] = { + [1] = DHCP_OPT_IPV4, /* Subnet Mask */ + [2] = DHCP_OPT_INT32, /* Time Offset */ + [3] = DHCP_OPT_IPV4_LIST, /* Router */ + [4] = DHCP_OPT_IPV4_LIST, /* Time Server */ + [5] = DHCP_OPT_IPV4_LIST, /* Name Server */ + [6] = DHCP_OPT_IPV4_LIST, /* Domain Name Server */ + [7] = DHCP_OPT_IPV4_LIST, /* Log Server */ + [8] = DHCP_OPT_IPV4_LIST, /* Cookie Server */ + [9] = DHCP_OPT_IPV4_LIST, /* LPR Server */ + [10] = DHCP_OPT_IPV4_LIST, /* Impress Server */ + [11] = DHCP_OPT_IPV4_LIST, /* Resource Location Server */ + [12] = DHCP_OPT_STR, /* Host Name */ + [13] = DHCP_OPT_UINT16, /* Boot File Size */ + [15] = DHCP_OPT_STR, /* Domain Name */ + [16] = DHCP_OPT_IPV4, /* Swap Server */ + [17] = DHCP_OPT_STR, /* Root Path */ + [19] = DHCP_OPT_UINT8, /* IP Forwarding */ + [23] = DHCP_OPT_UINT8, /* Default IP TTL */ + [26] = DHCP_OPT_UINT16, /* Interface MTU */ + [28] = DHCP_OPT_IPV4, /* Broadcast Address */ + [37] = DHCP_OPT_UINT8, /* TCP Default TTL */ + [38] = DHCP_OPT_UINT32, /* TCP Keepalive Interval */ + [40] = DHCP_OPT_STR, /* NIS Domain Name */ + [41] = DHCP_OPT_IPV4_LIST, /* NIS Servers */ + [42] = DHCP_OPT_IPV4_LIST, /* NTP Servers */ + [44] = DHCP_OPT_IPV4_LIST, /* NetBIOS Name Server */ + [50] = DHCP_OPT_IPV4, /* Requested IP Address */

Option 50 is client only. "This option is used in a client request (DHCPDISCOVER)"

...

+ [51] = DHCP_OPT_UINT32, /* IP Address Lease Time */ + [54] = DHCP_OPT_IPV4, /* Server Identifier */ + [57] = DHCP_OPT_UINT16, /* Max DHCP Message Size */

Option 57 is client only (See RFC 231 Table 3) Table 3: Fields and options used by DHCP servers Option DHCPOFFER DHCPACK DHCPNAK ------ --------- ------- ------- Requested IP address MUST NOT MUST NOT MUST NOT ... Maximum message size MUST NOT MUST NOT MUST NOT

...

+ [58] = DHCP_OPT_UINT32, /* Renewal (T1) Time */ + [59] = DHCP_OPT_UINT32, /* Rebinding (T2) Time */ + [60] = DHCP_OPT_STR, /* Vendor Class Identifier */ + [66] = DHCP_OPT_STR, /* TFTP Server Name */ + [67] = DHCP_OPT_STR, /* Bootfile Name */ + [252] = DHCP_OPT_STR, /* WPAD URL */ +}; + +/** + * dhcp_opt_parse() - Parse a DHCP option value + * @code: DHCP option code + * @str: Value string from command line + * @buf: Output buffer for binary value + * @buf_len: Size of output buffer + * + * Return: number of bytes written to @buf, or -1 on error + */ +static int dhcp_opt_parse(uint8_t code, const char *str, + uint8_t *buf, size_t buf_len) +{ + enum dhcp_opt_type type; + unsigned long val; + uint8_t width; + size_t slen; + size_t len; + char *end; + + if (code >= ARRAY_SIZE(dhcp_opt_types)) + return -1; + + type = dhcp_opt_types[code]; + + if (!*str) + return -1; + + switch (type) { + case DHCP_OPT_NONE: + return -1; + case DHCP_OPT_IPV4: + case DHCP_OPT_IPV4_LIST: + len = 0; + + do { + if (len + sizeof(struct in_addr) > buf_len) + return -1; + + if (!parse_ipv4(&str, + (struct in_addr *)(buf + len))) + return -1; + + len += sizeof(struct in_addr); + + if (type == DHCP_OPT_IPV4) + break; + } while (parse_literal(&str, ",")); + + if (!len || !parse_eoi(str)) + return -1; + + return len; + case DHCP_OPT_UINT8: + case DHCP_OPT_UINT16: + case DHCP_OPT_UINT32: + case DHCP_OPT_INT32: + if (type == DHCP_OPT_UINT8) + width = 1; + else if (type == DHCP_OPT_UINT16) + width = 2; + else + width = 4; + + if (buf_len < width) + return -1; + + errno = 0; + if (type == DHCP_OPT_INT32) { + long sval; + + sval = strtol(str, &end, 0); + if (*end || errno || + sval < INT32_MIN || sval > INT32_MAX) + return -1; + val = (uint32_t)sval; + } else { + val = strtoul(str, &end, 0); + if (*end || errno || + val >= (1ULL << (width * 8))) + return -1; + }

as for DHCPV6_OPT, you should use parse_unsigned()

...

+ + if (type == DHCP_OPT_UINT16) + *(uint16_t *)buf = htons(val); + else if (type == DHCP_OPT_UINT32 || + type == DHCP_OPT_INT32) + *(uint32_t *)buf = htonl(val);

Alignment issue, use temporary variable and then memcpy()

...

+ else + buf[0] = val; + + return width; + case DHCP_OPT_STR: + slen = strlen(str); + + if (slen >= buf_len)

It should be slen > buf_len as it's not nul terminated.

...

+ return -1; + + memcpy(buf, str, slen); + + return slen; + } + + return -1; +} + +/** + * dhcp_set_opt() - Parse and store a user-specified DHCP option + * @code: DHCP option code + * @val_str: Value string from command line + */ +void dhcp_set_opt(uint8_t code, const char *val_str) +{ + int ret; + + ret = dhcp_opt_parse(code, val_str, opts[code].s, sizeof(opts[code].s)); + if (ret < 0) + die("Invalid value for DHCP option %u: %s", code, val_str); + + opts[code].slen = ret; + opts[code].state = OPT_USER; +} + +/** + * dhcp_opt_to_str() - Render a binary DHCP option value to a printable string + * @code: DHCP option code + * @buf: Output string buffer + * @buf_len: Size of output buffer + * + * Return: pointer to @buf if option is set, NULL otherwise + */ +const char *dhcp_opt_to_str(uint8_t code, char *buf, size_t buf_len) +{ + enum dhcp_opt_type type; + unsigned int i; + int off = 0; + + if (opts[code].state == OPT_UNSET) + return NULL; + + assert(code < ARRAY_SIZE(dhcp_opt_types)); + + type = dhcp_opt_types[code]; + + switch (type) { + case DHCP_OPT_IPV4: + case DHCP_OPT_IPV4_LIST: + for (i = 0; i + sizeof(struct in_addr) <= (unsigned int)opts[code].slen; + i += sizeof(struct in_addr)) { + if (off) + off += snprintf(buf + off, buf_len - off, ","); + inet_ntop(AF_INET, opts[code].s + i, + buf + off, buf_len - off);

Same comment as for DHCPv6, check inet_ntop() return value (and you can avoid snprintf())

...

+ off = strlen(buf); + } + return buf; + case DHCP_OPT_UINT8: + case DHCP_OPT_UINT16: + case DHCP_OPT_UINT32: { + unsigned val = 0; + int j; + + for (j = 0; j < opts[code].slen; j++) + val = (val << 8) | opts[code].s[j];

Why don't we use ntohs() and ntohl()? To be sure slen is correctly handled?

...

+ + if (snprintf(buf, buf_len, "%u", val) >= (int)buf_len) + return NULL; + return buf; + } + case DHCP_OPT_INT32: { + int val = 0; + int j; + + for (j = 0; j < opts[code].slen; j++) + val = (val << 8) | opts[code].s[j];

well slen should 4 here as type is is DHCP_OPT_INT32, perhaps we can use ntohl()? (and check slen == 4).

...

+ + if (snprintf(buf, buf_len, "%d", val) >= (int)buf_len) + return NULL; > + return buf; + } + case DHCP_OPT_STR: + (void)snprintf(buf, buf_len, "%.*s", + opts[code].slen, opts[code].s); + return buf; + default: + assert(0); + } +} + /** * fill_one() - Fill a single option into a buffer * @buf: Buffer to write option @@ -474,14 +737,20 @@ int dhcp(const struct ctx *c, struct iov_tail *data) info(" from %s", eth_ntop(m->chaddr, macstr, sizeof(macstr)));

mask.s_addr = htonl(0xffffffff << (32 - c->ip4.prefix_len)); - memcpy(opts[1].s, &mask, sizeof(mask)); - memcpy(opts[3].s, &c->ip4.guest_gw, sizeof(c->ip4.guest_gw)); - memcpy(opts[54].s, &c->ip4.our_tap_addr, sizeof(c->ip4.our_tap_addr)); + if (opts[1].state != OPT_USER) + memcpy(opts[1].s, &mask, sizeof(mask)); + if (opts[3].state != OPT_USER) + memcpy(opts[3].s, &c->ip4.guest_gw, sizeof(c->ip4.guest_gw)); + if (opts[54].state != OPT_USER) { + memcpy(opts[54].s, &c->ip4.our_tap_addr, + sizeof(c->ip4.our_tap_addr)); + }

I think it would be more explicit to check for OPT_DEFAULT as we don't set it in opts[].state in the body of the condition statement.

...

/* If the gateway is not on the assigned subnet, send an option 121 * (Classless Static Routing) adding a dummy route to it. */ - if ((c->ip4.addr.s_addr & mask.s_addr) + if (opts[121].state != OPT_USER &&

Option 121 doesn't exist in dhcp_opt_types[] so user cannot set it (no need to check state).

...

+ (c->ip4.addr.s_addr & mask.s_addr) != (c->ip4.guest_gw.s_addr & mask.s_addr)) { /* a.b.c.d/32:0.0.0.0, 0:a.b.c.d */ opts[121].slen = 14; @@ -493,27 +762,31 @@ int dhcp(const struct ctx *c, struct iov_tail *data) &c->ip4.guest_gw, sizeof(c->ip4.guest_gw)); }

- if (c->mtu) { + if (opts[26].state != OPT_USER && c->mtu) { opts[26].slen = 2; opts[26].state = OPT_DEFAULT; opts[26].s[0] = c->mtu / 256; opts[26].s[1] = c->mtu % 256;

it's pre-existing, but it would be cleaner with: uint16_t mtu = htons(c->mtu); memcpy(opts[26].s, &mtu, sizeof(mtu);

...

}

- for (i = 0, opts[6].slen = 0; - !c->no_dhcp_dns && i < ARRAY_SIZE(c->ip4.dns); i++) { - if (IN4_IS_ADDR_UNSPECIFIED(&c->ip4.dns[i])) - break; - ((struct in_addr *)opts[6].s)[i] = c->ip4.dns[i]; - opts[6].slen += sizeof(uint32_t); + if (opts[6].state != OPT_USER) { + opts[6].slen = 0; + for (i = 0; + !c->no_dhcp_dns && i < ARRAY_SIZE(c->ip4.dns); + i++) { + if (IN4_IS_ADDR_UNSPECIFIED(&c->ip4.dns[i])) + break; + ((struct in_addr *)opts[6].s)[i] = c->ip4.dns[i]; + opts[6].slen += sizeof(uint32_t); + } + if (opts[6].slen) + opts[6].state = OPT_DEFAULT; + else + opts[6].state = OPT_UNSET; } - if (opts[6].slen) - opts[6].state = OPT_DEFAULT; - else - opts[6].state = OPT_UNSET;

opt_len = strlen(c->hostname); - if (opt_len > 0) { + if (opts[12].state != OPT_USER && opt_len > 0) { opts[12].slen = opt_len; opts[12].state = OPT_DEFAULT; memcpy(opts[12].s, &c->hostname, opt_len); diff --git a/dhcp.h b/dhcp.h index cd50c99..80abda6 100644 --- a/dhcp.h +++ b/dhcp.h @@ -8,5 +8,7 @@

int dhcp(const struct ctx *c, struct iov_tail *data); void dhcp_init(void); +void dhcp_set_opt(uint8_t code, const char *val_str); +const char *dhcp_opt_to_str(uint8_t code, char *buf, size_t buf_len);

#endif /* DHCP_H */ diff --git a/passt.1 b/passt.1 index 53e072a..b4a44c5 100644 --- a/passt.1 +++ b/passt.1 @@ -440,6 +440,48 @@ Send \fIname\fR as DHCP option 12 (hostname). FQDN to configure the client with. Send \fIname\fR as Client FQDN: DHCP option 81 and DHCPv6 option 39.

+.TP +.BR \-\-dhcp-opt " " \fICODE\fR,\fIVALUE\fR +Set DHCP option \fICODE\fR (1\-254) to \fIVALUE\fR. The value format depends +on the option type and is determined automatically from the option code. +Multiple IPv4 addresses are comma-separated. +This option can be specified multiple times. If the same option code is +given more than once, the last value wins. Options set with +\fB\-\-dhcp-opt\fR override built-in values. +.PP +Examples: +.nf + \-\-dhcp-opt 6,8.8.8.8,4.4.4.4 + \-\-dhcp-opt 12,myhostname +.fi +.PP +Only the following option codes are supported (unsupported codes cause an error): +.RS +.TP +.B IPv4 address options +1 (Subnet Mask), 16 (Swap Server), 28 (Broadcast Address), 50 (Requested IP),

Remove 50 (client only)

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+54 (Server Identifier) +.TP +.B IPv4 address list options (comma-separated) +3 (Router), 4 (Time Server), 5 (Name Server), 6 (DNS), 7 (Log Server), +8 (Cookie Server), 9 (LPR Server), 10 (Impress Server), +11 (Resource Location Server), 41 (NIS Servers), +42 (NTP Servers), 44 (NetBIOS Name Server) +.TP +.B Integer options +2 (Time Offset, 32-bit), 13 (Boot File Size, 16-bit), 19 (IP Forwarding, 8-bit), +23 (Default IP TTL, 8-bit), 26 (Interface MTU, 16-bit), +37 (TCP Default TTL, 8-bit), 38 (TCP Keepalive Interval, 32-bit), +51 (IP Address Lease Time, 32-bit), +57 (Max DHCP Message Size, 16-bit),

Remove 57 (Client only)

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+58 (Renewal Time, 32-bit), 59 (Rebinding Time, 32-bit) +.TP +.B String options +12 (Host Name), 15 (Domain Name), 17 (Root Path), 40 (NIS Domain Name), +60 (Vendor Class Identifier), 66 (TFTP Server Name), +67 (Bootfile Name), 252 (WPAD URL) +.RE + .TP .BR \-t ", " \-\-tcp-ports " " \fIspec Configure TCP port forwarding to guest or namespace. \fIspec\fR can be either:

Laurent Vivier

4:11 p.m.

New subject: [PATCH v6 6/6] dhcp: Add RFC 3396 option splitting for concatenation-requiring options

On 8/24/26 15:44, Anshu Kumari wrote:

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Implement option splitting per RFC 3396 for options that may exceed 255 bytes. A new concat_req[] lookup table marks options requiring concatenation (currently option 81, Client FQDN per RFC 4702).

The opts[].s buffer is resized from 255 to 497 bytes (OPT_CONCAT_MAX) to hold the maximum data that can be split across the options field, file field, and sname field.

When a concatenation-requiring option does not fit as a single option in any field, fill() calls fill_split() to split it across fields in RFC 3396 order: options field first, then file, then sname.

Link: https://bugs.passt.top/show_bug.cgi?id=192 Signed-off-by: Anshu Kumari --- v6: - Merged v5 patches 6/7 and 7/7 into a single patch. - Replaced DHCP_OPT_STR_CONCAT enum value and is_concat_opt() helper with a concat_req[] boolean lookup table. - Used MIN() macro instead of ternary for chunk size. - Fixed space calculation to account for 2-byte code+length overhead per chunk.

v5: - New patch: implement option splitting per RFC 3396 for options exceeding 255 bytes - Add DHCP_OPT_STR_CONCAT type, is_concat_opt(), fill_split() helpers - Resize opts[].s from 255 to OPT_CONCAT_MAX (497) bytes - Add /* fallthrough */ between DHCP_OPT_STR and DHCP_OPT_STR_CONCAT case --- dhcp.c | 99 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 98 insertions(+), 1 deletion(-)

diff --git a/dhcp.c b/dhcp.c index 43ce133..eda04d1 100644 --- a/dhcp.c +++ b/dhcp.c @@ -35,6 +35,11 @@ #include "dhcp.h" #include "parse.h"

+/* RFC 3396: maximum option data that can be split across options field, + * file field, and sname field (minus code+length overhead per portion). + */ +#define OPT_CONCAT_MAX 497 + /** * enum opt_state - DHCP option state * @OPT_UNSET: Option not configured @@ -59,7 +64,7 @@ enum opt_state { struct opt { int sent; int slen; - uint8_t s[255]; + uint8_t s[OPT_CONCAT_MAX]; int clen; uint8_t c[255]; enum opt_state state; @@ -215,6 +220,13 @@ static const enum dhcp_opt_type dhcp_opt_types[] = { [252] = DHCP_OPT_STR, /* WPAD URL */ };

+/** + * concat_req - Options requiring RFC 3396 concatenation, indexed by code + */ +static const bool concat_req[256] = { + [81] = true, /* Client FQDN (RFC 4702, Section 2) */ +}; + /** * dhcp_opt_parse() - Parse a DHCP option value * @code: DHCP option code @@ -309,6 +321,9 @@ static int dhcp_opt_parse(uint8_t code, const char *str, case DHCP_OPT_STR: slen = strlen(str);

+ if (!concat_req[code] && slen > 255) + return -1; + if (slen >= buf_len) return -1;

@@ -442,6 +457,40 @@ enum dhcp_overload { DHCP_OVERLOAD_SNAME = 2, };

+/** + * fill_split() - Write a split portion of an option into a buffer + * @buf: Buffer to write into + * @size: Usable size of @buf + * @o: Option number (code) + * @offset: Current offset within @buf, updated on write + * @data: Pointer to remaining option data to write + * @remaining: Bytes of option data still to write + * + * Return: number of data bytes written (excluding code+length header) + */ +static size_t fill_split(uint8_t *buf, size_t size, int o, int *offset, + const uint8_t *data, size_t remaining) +{ + size_t avail, chunk; + + if (*offset + 2 >= (int)size) + return 0; + + avail = size - *offset - 2; + chunk = MIN(remaining, avail); + if (!chunk) + return 0; + + buf[*offset] = o; + buf[*offset + 1] = chunk;

buf[] is uint8_t, but chunk can be > 255: avail can be OPT_MAX - 3 - 2 (302) remainining is, on first call opts[81].slen (that is opts[81].slen = strlen(c->fqdn) + 5, that can be PASST_MAXDNAME - 1 + 5 = 258). So to avoid this overflow (or other in future options) you should use chunk = MIN(MIN(remaining, avail), 255)

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+ *offset += 2; + + memcpy(buf + *offset, data, chunk); + *offset += chunk; + + return chunk; +} + /** * fill() - Fill options in message, with overload into file/sname if needed * @m: Message to fill @@ -495,6 +544,54 @@ static int fill(struct msg *m, enum dhcp_overload *overload, bool has_bootfile) } }

+ /* RFC 3396: split concatenation-requiring options that didn't fit + * as a single option. Split order: options, file, sname. + */ + for (o = 0; (size_t)o < ARRAY_SIZE(opts); o++) { + size_t file_cap, sname_cap, total, written; + + if (opts[o].state == OPT_UNSET || opts[o].sent || + !concat_req[o]) + continue; + + sname_cap = sizeof(m->sname) - 1 > (size_t)sname_off ? + sizeof(m->sname) - 1 - sname_off : 0; + + if (has_bootfile || sizeof(m->file) - 1 <= (size_t)file_off) + file_cap = 0; + else + file_cap = sizeof(m->file) - 1 - file_off; + + total = (size > (size_t)offset ? size - offset - 2 : 0)

here also 'size - offset - 2' must be capped by 255 otherwise total available space is not correctly evaluated.

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+ + (file_cap > 2 ? file_cap - 2 : 0) + + (sname_cap > 2 ? sname_cap - 2 : 0); + + if (total < (size_t)opts[o].slen) { + debug("DHCP: skipping option %i (no space to split)", + o); + continue; + } + + written = 0; + written += fill_split(m->o, size, o, &offset, + opts[o].s, opts[o].slen); + if (written < (size_t)opts[o].slen && !has_bootfile) + written += fill_split(m->file, + sizeof(m->file) - 1, o, + &file_off, + opts[o].s + written, + opts[o].slen - written); + if (written < (size_t)opts[o].slen) + written += fill_split(m->sname, + sizeof(m->sname) - 1, o, + &sname_off, + opts[o].s + written, + opts[o].slen - written); + + if (written >= (size_t)opts[o].slen) + opts[o].sent = 1; + } + /* Report any options that could not be sent */ for (o = 0; (size_t)o < ARRAY_SIZE(opts); o++) { if (opts[o].state != OPT_UNSET && !opts[o].sent)

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Anshu Kumari
Laurent Vivier