[PATCH v3 0/6] Add --dhcp-boot and --dhcp-opt options

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Anshu Kumari

1 Jun 2026 1 Jun '26

9:37 a.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. Anshu Kumari (6): conf: Add --dhcp-opt command-line option conf: Add --dhcp-boot command-line option dhcp: Add option type table and value parser dhcp: Refactor fill_one() to operate on a generic buffer dhcp: Add option overload doc: Add --dhcp-boot and --dhcp-opt to man page conf.c | 29 ++++- dhcp.c | 322 ++++++++++++++++++++++++++++++++++++++++++++++++++++---- dhcp.h | 1 + passt.1 | 41 ++++++++ passt.h | 16 +++ 5 files changed, 389 insertions(+), 20 deletions(-) -- 2.54.0

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Anshu Kumari

1 Jun 1 Jun

9:37 a.m.

New subject: [PATCH v3 1/6] conf: Add --dhcp-opt command-line option

Introduce the --dhcp-opt flag that allows setting arbitrary DHCP options from command-line in the form of [Option CODE,VALUE]. This patch adds the option storage in struct ctx and CLI parsing; the type-aware value parser and DHCP reply injection follow in subsequent patches. Link: https://bugs.passt.top/show_bug.cgi?id=192 Signed-off-by: Anshu Kumari --- v3: - Added dhcp_add_option() helper in dhcp.c for storing options with duplicate-code detection. - case 33 now calls dhcp_add_option() instead of inline storage. v2: - Added kerneldoc for @custom_opts, @custom_opts.code, @custom_opts.str, and @custom_opts_count in struct ctx - Removed len and val[255] fields from struct (moved to patch 3) - Removed braces from case 33, moved declarations (optcode, comma, end) to function scope - Renamed code → optcode to follow function-scope convention. --- conf.c | 24 +++++++++++++++++++++++- dhcp.c | 38 ++++++++++++++++++++++++++++++++++++++ dhcp.h | 1 + passt.h | 12 ++++++++++++ 4 files changed, 74 insertions(+), 1 deletion(-) diff --git a/conf.c b/conf.c index 029b9c7..ce78af1 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" @@ -616,7 +617,8 @@ 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 by code\n"); if (strstr(name, "pasta")) FPRINTF(f, " default: don't use any search list\n"); else @@ -844,6 +846,10 @@ static void conf_print(const struct ctx *c) info(" router: %s", inet_ntop(AF_INET, &c->ip4.guest_gw, buf, sizeof(buf))); + for (i = 0; i < c->custom_opts_count; i++) + info(" option %u: %s", + c->custom_opts[i].code, + c->custom_opts[i].str); } for (i = 0; i < ARRAY_SIZE(c->ip4.dns); i++) { @@ -1233,6 +1239,7 @@ void conf(struct ctx *c, int argc, char **argv) {"migrate-no-linger", no_argument, NULL, 30 }, {"stats", required_argument, NULL, 31 }, {"conf-path", required_argument, NULL, 'c' }, + {"dhcp-opt", required_argument, NULL, 33 }, { 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:"; @@ -1248,10 +1255,13 @@ void conf(struct ctx *c, int argc, char **argv) uint8_t prefix_len_from_opt = 0; unsigned int ifi4 = 0, ifi6 = 0; const char *logfile = NULL; + unsigned long optcode; char *runas = NULL; size_t logsize = 0; + const char *comma; long fd_tap_opt; int name, ret; + char *end; uid_t uid; gid_t gid; @@ -1465,6 +1475,18 @@ void conf(struct ctx *c, int argc, char **argv) die("Can't display statistics if not running in foreground"); c->stats = strtol(optarg, NULL, 0); break; + case 33: + comma = strchr(optarg, ','); + if (!comma) + die("--dhcp-opt requires CODE,VALUE format"); + + optcode = strtoul(optarg, &end, 0); + if (end != comma || optcode < 1 || optcode > 254) + die("DHCP option code must be 1-254: %s", + optarg); + + dhcp_add_option(c, optcode, comma + 1); + break; case 'd': c->debug = 1; c->quiet = 0; diff --git a/dhcp.c b/dhcp.c index 1ff8cba..c5fbf37 100644 --- a/dhcp.c +++ b/dhcp.c @@ -33,6 +33,44 @@ #include "log.h" #include "dhcp.h" + +/** + * dhcp_add_option() - Add or update a custom DHCP option + * @c: Execution context + * @code: DHCP option code + * @val_str: Value string from command line + * + * If @code was already added, the previous value is overwritten. + * Calls die() on any error. + * + * Return: 0 on success + */ +int dhcp_add_option(struct ctx *c, uint8_t code, const char *val_str) +{ + int idx; + + for (idx = 0; idx < c->custom_opts_count; idx++) { + if (c->custom_opts[idx].code == code) + break; + } + + if (idx == c->custom_opts_count) { + if (c->custom_opts_count >= MAX_CUSTOM_DHCP_OPTS) + die("Too many --dhcp-opt entries (max %d)", + MAX_CUSTOM_DHCP_OPTS); + c->custom_opts_count++; + } + + c->custom_opts[idx].code = code; + + if (snprintf_check(c->custom_opts[idx].str, + sizeof(c->custom_opts[0].str), + "%s", val_str)) + die("DHCP option value too long: %s", val_str); + + return 0; +} + /** * struct opt - DHCP option * @sent: Convenience flag, set while filling replies diff --git a/dhcp.h b/dhcp.h index cd50c99..9c8f1e3 100644 --- a/dhcp.h +++ b/dhcp.h @@ -8,5 +8,6 @@ int dhcp(const struct ctx *c, struct iov_tail *data); void dhcp_init(void); +int dhcp_add_option(struct ctx *c, uint8_t code, const char *val_str); #endif /* DHCP_H */ diff --git a/passt.h b/passt.h index 1726965..3a0816f 100644 --- a/passt.h +++ b/passt.h @@ -182,6 +182,10 @@ struct ip6_ctx { * @dns_search: DNS search list * @hostname: Guest hostname * @fqdn: Guest FQDN + * @custom_opts: User-specified DHCP options from --dhcp-opt + * @custom_opts.code: DHCP option code + * @custom_opts.str: Original string value from command line + * @custom_opts_count: Number of entries in @custom_opts * @ifi6: Template interface for IPv6, -1: none, 0: IPv6 disabled * @ip6: IPv6 configuration * @pasta_ifn: Name of namespace interface for pasta @@ -263,6 +267,14 @@ struct ctx { char hostname[PASST_MAXDNAME]; char fqdn[PASST_MAXDNAME]; +#define MAX_CUSTOM_DHCP_OPTS 32 + + struct { + uint8_t code; + char str[256]; + } custom_opts[MAX_CUSTOM_DHCP_OPTS]; + int custom_opts_count; + int ifi6; struct ip6_ctx ip6; -- 2.54.0

Anshu Kumari

9:37 a.m.

New subject: [PATCH v3 2/6] conf: Add --dhcp-boot command-line option

Introduce the --dhcp-boot flag that sets the boot file URL for network boot specially for ipxe. This patch adds the option storage and CLI parsing. Link: https://bugs.passt.top/show_bug.cgi?id=192 Signed-off-by: Anshu Kumari --- 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 +++++ 1 file changed, 5 insertions(+) diff --git a/conf.c b/conf.c index ce78af1..f7281e2 100644 --- a/conf.c +++ b/conf.c @@ -618,6 +618,7 @@ 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 URL Boot file URL for network boot\n" " --dhcp-opt CODE,VAL Set DHCP option by code\n"); if (strstr(name, "pasta")) FPRINTF(f, " default: don't use any search list\n"); @@ -1239,6 +1240,7 @@ void conf(struct ctx *c, int argc, char **argv) {"migrate-no-linger", no_argument, NULL, 30 }, {"stats", required_argument, NULL, 31 }, {"conf-path", required_argument, NULL, 'c' }, + {"dhcp-boot", required_argument, NULL, 32 }, {"dhcp-opt", required_argument, NULL, 33 }, { 0 }, }; @@ -1475,6 +1477,9 @@ void conf(struct ctx *c, int argc, char **argv) die("Can't display statistics if not running in foreground"); c->stats = strtol(optarg, NULL, 0); break; + case 32: + dhcp_add_option(c, 67, optarg); + break; case 33: comma = strchr(optarg, ','); if (!comma) -- 2.54.0

Anshu Kumari

9:37 a.m.

New subject: [PATCH v3 3/6] dhcp: Add option type table and value parser

Add an RFC 2132 type lookup table mapping DHCP option codes to their expected value formats, and a dhcp_opt_parse() function that converts CLI string values into their binary wire representation. Wire dhcp_opt_parse() into dhcp_add_option() so that values are validated and encoded at configuration time. Link: https://bugs.passt.top/show_bug.cgi?id=192 Signed-off-by: Anshu Kumari --- 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. --- dhcp.c | 180 +++++++++++++++++++++++++++++++++++++++++++++++++++++++- passt.h | 4 ++ 2 files changed, 181 insertions(+), 3 deletions(-) diff --git a/dhcp.c b/dhcp.c index c5fbf37..07a42b9 100644 --- a/dhcp.c +++ b/dhcp.c @@ -23,6 +23,7 @@ #include #include #include +#include #include "util.h" #include "ip.h" @@ -33,6 +34,170 @@ #include "log.h" #include "dhcp.h" +/** + * 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_INT8: Unsigned 8-bit integer + * @DHCP_OPT_INT16: Unsigned 16-bit integer + * @DHCP_OPT_INT32: Unsigned 32-bit integer + */ +enum dhcp_opt_type { + DHCP_OPT_NONE, + DHCP_OPT_STR, + DHCP_OPT_IPV4, + DHCP_OPT_IPV4_LIST, + DHCP_OPT_INT8, + DHCP_OPT_INT16, + 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[256] = { + [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_INT16, /* Boot File Size */ + [15] = DHCP_OPT_STR, /* Domain Name */ + [16] = DHCP_OPT_IPV4, /* Swap Server */ + [17] = DHCP_OPT_STR, /* Root Path */ + [19] = DHCP_OPT_INT8, /* IP Forwarding */ + [23] = DHCP_OPT_INT8, /* Default IP TTL */ + [26] = DHCP_OPT_INT16, /* Interface MTU */ + [28] = DHCP_OPT_IPV4, /* Broadcast Address */ + [37] = DHCP_OPT_INT8, /* TCP Default TTL */ + [38] = DHCP_OPT_INT32, /* 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_INT32, /* IP Address Lease Time */ + [53] = DHCP_OPT_INT8, /* DHCP Message Type */ + [54] = DHCP_OPT_IPV4, /* Server Identifier */ + [57] = DHCP_OPT_INT16, /* Max DHCP Message Size */ + [58] = DHCP_OPT_INT32, /* Renewal (T1) Time */ + [59] = DHCP_OPT_INT32, /* 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 = dhcp_opt_types[code]; + char *tok, *saveptr, *end; + struct in_addr addr; + unsigned long val; + unsigned int i; + uint8_t width; + char tmp[256]; + size_t slen; + int len; + + if (!*str) + die("Empty value for DHCP option %u", code); + + switch (type) { + case DHCP_OPT_NONE: + die("Unsupported DHCP option: %u," + " see passt(1) for supported codes", code); + case DHCP_OPT_IPV4: + case DHCP_OPT_IPV4_LIST: + len = 0; + + /* Reject empty, leading/trailing, or consecutive commas */ + if (!*str || *str == ',' || str[strlen(str) - 1] == ',' || + strstr(str, ",,")) + return -1; + + if (snprintf_check(tmp, sizeof(tmp), "%s", str)) + return -1; + + for (tok = strtok_r(tmp, ",", &saveptr); tok; + tok = strtok_r(NULL, ",", &saveptr)) { + if (inet_pton(AF_INET, tok, &addr) != 1) + return -1; + + if (len + (int)sizeof(addr) > (int)buf_len) + return -1; + + memcpy(buf + len, &addr, sizeof(addr)); + len += sizeof(addr); + + if (type == DHCP_OPT_IPV4) + break; + } + + if (type == DHCP_OPT_IPV4 && strtok_r(NULL, ",", &saveptr)) + return -1; + + return len; + case DHCP_OPT_INT8: + case DHCP_OPT_INT16: + case DHCP_OPT_INT32: + if (type == DHCP_OPT_INT8) + width = 1; + else if (type == DHCP_OPT_INT16) + width = 2; + else + width = 4; + + errno = 0; + val = strtoul(str, &end, 0); + + if (*end || errno) + return -1; + + if (buf_len < width) + return -1; + + if (val >= (1ULL << (width * 8))) + return -1; + + for (i = width; i > 0; i--) { + buf[i - 1] = val & 0xff; + val >>= 8; + } + + return width; + case DHCP_OPT_STR: + slen = strlen(str); + + if (!slen || slen >= buf_len) + return -1; + + memcpy(buf, str, slen); + + return slen; + } + + return -1; +} /** * dhcp_add_option() - Add or update a custom DHCP option @@ -40,14 +205,15 @@ * @code: DHCP option code * @val_str: Value string from command line * - * If @code was already added, the previous value is overwritten. - * Calls die() on any error. + * Parses @val_str according to the type registered for @code in + * dhcp_opt_types[]. If @code was already added, the previous value + * is overwritten. Calls die() on any error. * * Return: 0 on success */ int dhcp_add_option(struct ctx *c, uint8_t code, const char *val_str) { - int idx; + int idx, ret; for (idx = 0; idx < c->custom_opts_count; idx++) { if (c->custom_opts[idx].code == code) @@ -61,7 +227,15 @@ int dhcp_add_option(struct ctx *c, uint8_t code, const char *val_str) c->custom_opts_count++; } + ret = dhcp_opt_parse(code, val_str, + c->custom_opts[idx].val, + sizeof(c->custom_opts[0].val)); + if (ret < 0) + die("Invalid value for DHCP option %u: %s", + code, val_str); + c->custom_opts[idx].code = code; + c->custom_opts[idx].len = ret; if (snprintf_check(c->custom_opts[idx].str, sizeof(c->custom_opts[0].str), diff --git a/passt.h b/passt.h index 3a0816f..751fee3 100644 --- a/passt.h +++ b/passt.h @@ -184,6 +184,8 @@ struct ip6_ctx { * @fqdn: Guest FQDN * @custom_opts: User-specified DHCP options from --dhcp-opt * @custom_opts.code: DHCP option code + * @custom_opts.len: Length of binary value in @val + * @custom_opts.val: Binary-encoded option value * @custom_opts.str: Original string value from command line * @custom_opts_count: Number of entries in @custom_opts * @ifi6: Template interface for IPv6, -1: none, 0: IPv6 disabled @@ -271,6 +273,8 @@ struct ctx { struct { uint8_t code; + uint8_t len; + uint8_t val[255]; char str[256]; } custom_opts[MAX_CUSTOM_DHCP_OPTS]; int custom_opts_count; -- 2.54.0

Anshu Kumari

9:37 a.m.

New subject: [PATCH v3 4/6] 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 --- 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 | 25 +++++++++++++------------ 1 file changed, 13 insertions(+), 12 deletions(-) diff --git a/dhcp.c b/dhcp.c index 07a42b9..5c6a492 100644 --- a/dhcp.c +++ b/dhcp.c @@ -343,28 +343,29 @@ 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 + 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; @@ -389,19 +390,19 @@ 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)) + 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); } -- 2.54.0

Anshu Kumari

9:37 a.m.

New subject: [PATCH v3 5/6] dhcp: Add option overload

A user can enter lots of options in command-line which may not fit in existing buffer, So when the options field is full, overflow remaining DHCP options into the file and sname fields per RFC 2132 option 52. Also, when the file field is not used for overload, copy the boot file URL there directly for legacy PXE clients. Link: https://bugs.passt.top/show_bug.cgi?id=192 Signed-off-by: Anshu Kumari --- 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 | 91 +++++++++++++++++++++++++++++++++++++++++++++++++++------- 1 file changed, 81 insertions(+), 10 deletions(-) diff --git a/dhcp.c b/dhcp.c index 5c6a492..a9d56fd 100644 --- a/dhcp.c +++ b/dhcp.c @@ -372,14 +372,64 @@ static bool fill_one(uint8_t *buf, size_t size, int o, int *offset) return false; } +/* RFC 2132, Section 9.3 - Option Overload*/ +#define DHCP_OVERLOAD_FILE 1 +#define DHCP_OVERLOAD_SNAME 2 + /** - * fill() - Fill options in message + * fill_overflow() - Fill remaining options into sname and file fields + * @m: Message whose sname/file fields may be used for overflow + * + * Try the smaller sname field first: small options go there, leaving + * the larger file field available for big options and for the boot + * file name (option 67) if set. + * + * Return: option 52 overload value: 0 if no overflow, + * DHCP_OVERLOAD_FILE for file, DHCP_OVERLOAD_SNAME for sname, + * or both OR'd together + */ +static int fill_overflow(struct msg *m) +{ + int sname_off = 0, file_off = 0, overload = 0; + int o; + + for (o = 0; (size_t)o < ARRAY_SIZE(opts); o++) { + if (opts[o].slen == -1 || opts[o].sent) + continue; + fill_one(m->sname, sizeof(m->sname) - 1, o, &sname_off); + } + + for (o = 0; (size_t)o < ARRAY_SIZE(opts); o++) { + if (opts[o].slen == -1 || opts[o].sent) + continue; + if (fill_one(m->file, sizeof(m->file) - 1, o, &file_off)) + debug("DHCP: skipping option %i (overload full)", 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; + } + + return overload; +} + +/** + * 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) * * Return: current size of options field */ -static int fill(struct msg *m) +static int fill(struct msg *m, int *overload) { + /* Reserve 3 bytes for option 52 (overload) if needed */ + size_t size = OPT_MAX - 3; int i, o, offset = 0; for (o = 0; o < 255; o++) @@ -390,20 +440,25 @@ 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].slen != -1) - 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].slen != -1 && !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); + } + + *overload = fill_overflow(m); + + if (*overload) { + m->o[offset++] = 52; + m->o[offset++] = 1; + m->o[offset++] = *overload; } m->o[offset++] = 255; @@ -528,6 +583,7 @@ int dhcp(const struct ctx *c, struct iov_tail *data) struct msg const *m; struct msg reply; unsigned int i; + int overload; eh = IOV_REMOVE_HEADER(data, eh_storage); iph = IOV_PEEK_HEADER(data, iph_storage); @@ -677,9 +733,24 @@ int dhcp(const struct ctx *c, struct iov_tail *data) } if (!c->no_dhcp_dns_search) - opt_set_dns_search(c, sizeof(m->o)); + opt_set_dns_search(c, OPT_MAX - 3); + + for (i = 0; i < (unsigned int)c->custom_opts_count; i++) { + uint8_t code = c->custom_opts[i].code; + + opts[code].slen = c->custom_opts[i].len; + memcpy(opts[code].s, c->custom_opts[i].val, + c->custom_opts[i].len); + } + + dlen = offsetof(struct msg, o) + fill(&reply, &overload); - dlen = offsetof(struct msg, o) + fill(&reply); + /* Copy boot file name into the file field for legacy PXE clients, + * unless the file field is already used for option overload. + */ + if (!(overload & DHCP_OVERLOAD_FILE) && + opts[67].slen > 0 && (size_t)opts[67].slen < sizeof(reply.file)) + memcpy(reply.file, opts[67].s, opts[67].slen); if (m->flags & FLAG_BROADCAST) dst = in4addr_broadcast; -- 2.54.0

Anshu Kumari

9:37 a.m.

New subject: [PATCH v3 6/6] doc: Add --dhcp-boot and --dhcp-opt to man page

Document the new --dhcp-boot and --dhcp-opt command-line options in the passt(1) man page, including supported option codes grouped by value type and usage examples. Link: https://bugs.passt.top/show_bug.cgi?id=192 Signed-off-by: Anshu Kumari --- v3: - Removed options 33, 55, 61, 119 from supported codes list - Added note: "If the same name option code is given more than once, the last value wins". v2: - Updated --dhcp-boot description. - Highlighted cross-referenced options with \fB...\fR. - Updated IP list format from "space-separated within quotes" to "comma-separated". - option 121 dropped. - Added option 55 to string options list. - Removed --dhcp-boot override reference from --dhcp-opt description. --- passt.1 | 41 +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 41 insertions(+) diff --git a/passt.1 b/passt.1 index 908fd4a..57e2cc1 100644 --- a/passt.1 +++ b/passt.1 @@ -430,6 +430,47 @@ 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 " " \fIurl +Convenience shorthand for \fB\-\-dhcp-opt\fR 67,\fIurl\fR. +Sets the boot file name (DHCP option 67) for network boot. +For UEFI HTTP boot, also set the vendor class identifier using +\fB\-\-dhcp-opt\fR 60,HTTPClient. + +.TP +.BR \-\-dhcp-opt " " \fICODE\fR,\fIVALUE\fR +Set a DHCP option by numeric code. The value format 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. +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), +53 (DHCP Message Type, 8-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 one of: -- 2.54.0

David Gibson

2 Jun 2 Jun

4:23 a.m.

New subject: [PATCH v3 3/6] dhcp: Add option type table and value parser

On Mon, Jun 01, 2026 at 01:07:53PM +0530, Anshu Kumari wrote:

...

Add an RFC 2132 type lookup table mapping DHCP option codes to their expected value formats, and a dhcp_opt_parse() function that converts CLI string values into their binary wire representation.

Wire dhcp_opt_parse() into dhcp_add_option() so that values are validated and encoded at configuration time.

Link: https://bugs.passt.top/show_bug.cgi?id=192 Signed-off-by: Anshu Kumari --- 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.

Thanks for the detailed changelogs, by the way. I know these are a bunch of work to maintain, but they really help when reviewing.

...

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. --- dhcp.c | 180 +++++++++++++++++++++++++++++++++++++++++++++++++++++++- passt.h | 4 ++ 2 files changed, 181 insertions(+), 3 deletions(-)

diff --git a/dhcp.c b/dhcp.c index c5fbf37..07a42b9 100644 --- a/dhcp.c +++ b/dhcp.c @@ -23,6 +23,7 @@ #include #include #include +#include

#include "util.h" #include "ip.h" @@ -33,6 +34,170 @@ #include "log.h" #include "dhcp.h"

+/** + * 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_INT8: Unsigned 8-bit integer + * @DHCP_OPT_INT16: Unsigned 16-bit integer + * @DHCP_OPT_INT32: Unsigned 32-bit integer + */ +enum dhcp_opt_type { + DHCP_OPT_NONE, + DHCP_OPT_STR, + DHCP_OPT_IPV4, + DHCP_OPT_IPV4_LIST, + DHCP_OPT_INT8, + DHCP_OPT_INT16, + 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[256] = { + [1] = DHCP_OPT_IPV4, /* Subnet Mask */ + [2] = DHCP_OPT_INT32, /* Time Offset */ + [3] = DHCP_OPT_IPV4_LIST, /* Router */

I'm still a bit unsure if we want to allow user modification of the options, like this one, which we already manage ourselves.

...

+ [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_INT16, /* Boot File Size */ + [15] = DHCP_OPT_STR, /* Domain Name */ + [16] = DHCP_OPT_IPV4, /* Swap Server */ + [17] = DHCP_OPT_STR, /* Root Path */ + [19] = DHCP_OPT_INT8, /* IP Forwarding */ + [23] = DHCP_OPT_INT8, /* Default IP TTL */ + [26] = DHCP_OPT_INT16, /* Interface MTU */ + [28] = DHCP_OPT_IPV4, /* Broadcast Address */ + [37] = DHCP_OPT_INT8, /* TCP Default TTL */ + [38] = DHCP_OPT_INT32, /* 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_INT32, /* IP Address Lease Time */ + [53] = DHCP_OPT_INT8, /* DHCP Message Type */ + [54] = DHCP_OPT_IPV4, /* Server Identifier */ + [57] = DHCP_OPT_INT16, /* Max DHCP Message Size */ + [58] = DHCP_OPT_INT32, /* Renewal (T1) Time */ + [59] = DHCP_OPT_INT32, /* 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 = dhcp_opt_types[code]; + char *tok, *saveptr, *end; + struct in_addr addr; + unsigned long val; + unsigned int i; + uint8_t width; + char tmp[256]; + size_t slen; + int len; + + if (!*str) + die("Empty value for DHCP option %u", code); + + switch (type) { + case DHCP_OPT_NONE: + die("Unsupported DHCP option: %u," + " see passt(1) for supported codes", code); + case DHCP_OPT_IPV4: + case DHCP_OPT_IPV4_LIST: + len = 0; + + /* Reject empty, leading/trailing, or consecutive commas */ + if (!*str || *str == ',' || str[strlen(str) - 1] == ',' || + strstr(str, ",,")) + return -1; + + if (snprintf_check(tmp, sizeof(tmp), "%s", str)) + return -1;

The arbitrary 256 byte buffer limit here isn't great. The string encoding of an IPv4 address can be nearly 4 times as long as the binary encoding, so we could potentially hit this with a longish, but not ridiculous address list.

...

+ for (tok = strtok_r(tmp, ",", &saveptr); tok; + tok = strtok_r(NULL, ",", &saveptr)) {

One way to avoid that would be to avoid using strtok_r() which relies in in-place modifying the input. Instead you'd need to repeatedly find the length of the next chunk with strchr() or strcpsn(), then extract each one into a tmp of length INET_ADDRSTRLEN to call inet_pton(). On the plus side, that should naturally deal with the case of extraneous commas (it would show up as an empth entry), rather than requiring an explicit check at the top.

...

+ if (inet_pton(AF_INET, tok, &addr) != 1) + return -1; + + if (len + (int)sizeof(addr) > (int)buf_len) + return -1;

You could make this check before the inet_pton(), then do the conversion directly into buf, avoiding the addr temporary.

...

+ + memcpy(buf + len, &addr, sizeof(addr)); + len += sizeof(addr); + + if (type == DHCP_OPT_IPV4) + break; + } + + if (type == DHCP_OPT_IPV4 && strtok_r(NULL, ",", &saveptr)) + return -1; + + return len; + case DHCP_OPT_INT8: + case DHCP_OPT_INT16: + case DHCP_OPT_INT32: + if (type == DHCP_OPT_INT8) + width = 1; + else if (type == DHCP_OPT_INT16) + width = 2; + else + width = 4; + + errno = 0; + val = strtoul(str, &end, 0); + + if (*end || errno) + return -1; + + if (buf_len < width) + return -1; + + if (val >= (1ULL << (width * 8))) + return -1; + + for (i = width; i > 0; i--) { + buf[i - 1] = val & 0xff; + val >>= 8; + } + + return width; + case DHCP_OPT_STR: + slen = strlen(str); + + if (!slen || slen >= buf_len) + return -1; + + memcpy(buf, str, slen);

Do you need to include the terminating \0 here? If so you'll need slen + 1.

...

+ + return slen; + } + + return -1; +}

/** * dhcp_add_option() - Add or update a custom DHCP option @@ -40,14 +205,15 @@ * @code: DHCP option code * @val_str: Value string from command line * - * If @code was already added, the previous value is overwritten. - * Calls die() on any error. + * Parses @val_str according to the type registered for @code in + * dhcp_opt_types[]. If @code was already added, the previous value + * is overwritten. Calls die() on any error. * * Return: 0 on success */ int dhcp_add_option(struct ctx *c, uint8_t code, const char *val_str) { - int idx; + int idx, ret;

for (idx = 0; idx < c->custom_opts_count; idx++) { if (c->custom_opts[idx].code == code) @@ -61,7 +227,15 @@ int dhcp_add_option(struct ctx *c, uint8_t code, const char *val_str) c->custom_opts_count++; }

+ ret = dhcp_opt_parse(code, val_str, + c->custom_opts[idx].val, + sizeof(c->custom_opts[0].val));

Now that this parsing and adding code is all in dhcp.c, could we parse the options directly into the existing opts[] global, rather than requiring both the string and parsed forms in c->custom_opts?

...

+ if (ret < 0) + die("Invalid value for DHCP option %u: %s", + code, val_str); + c->custom_opts[idx].code = code; + c->custom_opts[idx].len = ret;

if (snprintf_check(c->custom_opts[idx].str, sizeof(c->custom_opts[0].str), diff --git a/passt.h b/passt.h index 3a0816f..751fee3 100644 --- a/passt.h +++ b/passt.h @@ -184,6 +184,8 @@ struct ip6_ctx { * @fqdn: Guest FQDN * @custom_opts: User-specified DHCP options from --dhcp-opt * @custom_opts.code: DHCP option code + * @custom_opts.len: Length of binary value in @val + * @custom_opts.val: Binary-encoded option value * @custom_opts.str: Original string value from command line * @custom_opts_count: Number of entries in @custom_opts * @ifi6: Template interface for IPv6, -1: none, 0: IPv6 disabled @@ -271,6 +273,8 @@ struct ctx {

struct { uint8_t code; + uint8_t len; + uint8_t val[255]; char str[256]; } custom_opts[MAX_CUSTOM_DHCP_OPTS]; int custom_opts_count; -- 2.54.0

-- David Gibson (he or they) | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you, not the other way | around. http://www.ozlabs.org/~dgibson

David Gibson

4 a.m.

New subject: [PATCH v3 1/6] conf: Add --dhcp-opt command-line option

On Mon, Jun 01, 2026 at 01:07:51PM +0530, Anshu Kumari wrote:

...

Introduce the --dhcp-opt flag that allows setting arbitrary DHCP options from command-line in the form of [Option CODE,VALUE]. This patch adds the option storage in struct ctx and CLI parsing; the type-aware value parser and DHCP reply injection follow in subsequent patches.

Link: https://bugs.passt.top/show_bug.cgi?id=192 Signed-off-by: Anshu Kumari

LGTM except for one remaining detail [snip]

...

@@ -1465,6 +1475,18 @@ void conf(struct ctx *c, int argc, char **argv) die("Can't display statistics if not running in foreground"); c->stats = strtol(optarg, NULL, 0); break; + case 33: + comma = strchr(optarg, ','); + if (!comma) + die("--dhcp-opt requires CODE,VALUE format"); + + optcode = strtoul(optarg, &end, 0);

Sorry, missed it on the previous round of review. This strtoul() also needs the errno = 0 / check errno trick to catch the handful of error cases that end != comma won't.

...

+ if (end != comma || optcode < 1 || optcode > 254) + die("DHCP option code must be 1-254: %s", + optarg); + + dhcp_add_option(c, optcode, comma + 1); + break; case 'd': c->debug = 1; c->quiet = 0; diff --git a/dhcp.c b/dhcp.c index 1ff8cba..c5fbf37 100644 --- a/dhcp.c +++ b/dhcp.c @@ -33,6 +33,44 @@ #include "log.h" #include "dhcp.h"

+ +/** + * dhcp_add_option() - Add or update a custom DHCP option + * @c: Execution context + * @code: DHCP option code + * @val_str: Value string from command line + * + * If @code was already added, the previous value is overwritten. + * Calls die() on any error. + * + * Return: 0 on success + */ +int dhcp_add_option(struct ctx *c, uint8_t code, const char *val_str) +{ + int idx; + + for (idx = 0; idx < c->custom_opts_count; idx++) { + if (c->custom_opts[idx].code == code) + break; + } + + if (idx == c->custom_opts_count) { + if (c->custom_opts_count >= MAX_CUSTOM_DHCP_OPTS) + die("Too many --dhcp-opt entries (max %d)", + MAX_CUSTOM_DHCP_OPTS); + c->custom_opts_count++; + } + + c->custom_opts[idx].code = code; + + if (snprintf_check(c->custom_opts[idx].str, + sizeof(c->custom_opts[0].str), + "%s", val_str)) + die("DHCP option value too long: %s", val_str); + + return 0; +} + /** * struct opt - DHCP option * @sent: Convenience flag, set while filling replies diff --git a/dhcp.h b/dhcp.h index cd50c99..9c8f1e3 100644 --- a/dhcp.h +++ b/dhcp.h @@ -8,5 +8,6 @@

int dhcp(const struct ctx *c, struct iov_tail *data); void dhcp_init(void); +int dhcp_add_option(struct ctx *c, uint8_t code, const char *val_str);

#endif /* DHCP_H */ diff --git a/passt.h b/passt.h index 1726965..3a0816f 100644 --- a/passt.h +++ b/passt.h @@ -182,6 +182,10 @@ struct ip6_ctx { * @dns_search: DNS search list * @hostname: Guest hostname * @fqdn: Guest FQDN + * @custom_opts: User-specified DHCP options from --dhcp-opt + * @custom_opts.code: DHCP option code + * @custom_opts.str: Original string value from command line + * @custom_opts_count: Number of entries in @custom_opts * @ifi6: Template interface for IPv6, -1: none, 0: IPv6 disabled * @ip6: IPv6 configuration * @pasta_ifn: Name of namespace interface for pasta @@ -263,6 +267,14 @@ struct ctx { char hostname[PASST_MAXDNAME]; char fqdn[PASST_MAXDNAME];

+#define MAX_CUSTOM_DHCP_OPTS 32 + + struct { + uint8_t code; + char str[256]; + } custom_opts[MAX_CUSTOM_DHCP_OPTS]; + int custom_opts_count; + int ifi6; struct ip6_ctx ip6;

-- 2.54.0

-- David Gibson (he or they) | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you, not the other way | around. http://www.ozlabs.org/~dgibson

David Gibson

4:02 a.m.

New subject: [PATCH v3 2/6] conf: Add --dhcp-boot command-line option

On Mon, Jun 01, 2026 at 01:07:52PM +0530, Anshu Kumari wrote:

...

Introduce the --dhcp-boot flag that sets the boot file URL for network boot specially for ipxe. This patch adds the option storage and CLI parsing.

Link: https://bugs.passt.top/show_bug.cgi?id=192 Signed-off-by: Anshu Kumari

Reviewed-by: David Gibson

...

--- 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 +++++ 1 file changed, 5 insertions(+)

diff --git a/conf.c b/conf.c index ce78af1..f7281e2 100644 --- a/conf.c +++ b/conf.c @@ -618,6 +618,7 @@ 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 URL Boot file URL for network boot\n" " --dhcp-opt CODE,VAL Set DHCP option by code\n"); if (strstr(name, "pasta")) FPRINTF(f, " default: don't use any search list\n"); @@ -1239,6 +1240,7 @@ void conf(struct ctx *c, int argc, char **argv) {"migrate-no-linger", no_argument, NULL, 30 }, {"stats", required_argument, NULL, 31 }, {"conf-path", required_argument, NULL, 'c' }, + {"dhcp-boot", required_argument, NULL, 32 }, {"dhcp-opt", required_argument, NULL, 33 }, { 0 }, }; @@ -1475,6 +1477,9 @@ void conf(struct ctx *c, int argc, char **argv) die("Can't display statistics if not running in foreground"); c->stats = strtol(optarg, NULL, 0); break; + case 32: + dhcp_add_option(c, 67, optarg); + break; case 33: comma = strchr(optarg, ','); if (!comma) -- 2.54.0

-- David Gibson (he or they) | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you, not the other way | around. http://www.ozlabs.org/~dgibson

David Gibson

4:25 a.m.

New subject: [PATCH v3 4/6] dhcp: Refactor fill_one() to operate on a generic buffer

On Mon, Jun 01, 2026 at 01:07:54PM +0530, 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

Reviewed-by: David Gibson

...

--- 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 | 25 +++++++++++++------------ 1 file changed, 13 insertions(+), 12 deletions(-)

diff --git a/dhcp.c b/dhcp.c index 07a42b9..5c6a492 100644 --- a/dhcp.c +++ b/dhcp.c @@ -343,28 +343,29 @@ 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 + 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; @@ -389,19 +390,19 @@ 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)) + 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); }

-- 2.54.0

-- David Gibson (he or they) | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you, not the other way | around. http://www.ozlabs.org/~dgibson

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