[PATCH v3 0/3] dhcp: Add support for Rapid Commit, broadcast replies
These are all changes coming from pending muvm experiments where I'm trying to speed up and simplify the networking setup in the guest. v3: In 1/3, set 'slen' for options we won't send to -1 in dhcp_init(), and reset it for option 80 every time we handle a DHCP request. Add a comment about DHCP needing a valid message type (option 53) v2: In 3/3, add in4addr_broadcast to ip.h, instead of open-coding it in dhcp() Stefano Brivio (3): dhcp: Use -1 as "missing option" length instead of 0 dhcp: Introduce support for Rapid Commit (option 80, RFC 4039) dhcp: Honour broadcast flag (RFC 2131, 4.1) dhcp.c | 51 ++++++++++++++++++++++++++++++++++++++++----------- ip.h | 3 +++ 2 files changed, 43 insertions(+), 11 deletions(-) -- 2.43.0
We want to add support for option 80 (Rapid Commit, RFC 4039), whose
length is 0.
Signed-off-by: Stefano Brivio
On Mon, Nov 25, 2024 at 04:28:10PM +0100, Stefano Brivio wrote:
We want to add support for option 80 (Rapid Commit, RFC 4039), whose length is 0.
Signed-off-by: Stefano Brivio
Reviewed-by: David Gibson
--- dhcp.c | 28 +++++++++++++++++++++------- 1 file changed, 21 insertions(+), 7 deletions(-)
diff --git a/dhcp.c b/dhcp.c index a06f143..57f69a5 100644 --- a/dhcp.c +++ b/dhcp.c @@ -36,9 +36,9 @@ /** * struct opt - DHCP option * @sent: Convenience flag, set while filling replies - * @slen: Length of option defined for server + * @slen: Length of option defined for server, -1 if not going to be sent * @s: Option payload from server - * @clen: Length of option received from client + * @clen: Length of option received from client, -1 if not received * @c: Option payload from client */ struct opt { @@ -68,6 +68,11 @@ static struct opt opts[255]; */ 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, @@ -154,17 +159,17 @@ static int fill(struct msg *m) * option 53 at the beginning of the list. * Put it there explicitly, unless requested via option 55. */ - if (!memchr(opts[55].c, 53, opts[55].clen)) + if (opts[55].clen > 0 && !memchr(opts[55].c, 53, opts[55].clen)) fill_one(m, 53, &offset);
for (i = 0; i < opts[55].clen; i++) { o = opts[55].c[i]; - if (opts[o].slen) + if (opts[o].slen != -1) fill_one(m, o, &offset); }
for (o = 0; o < 255; o++) { - if (opts[o].slen && !opts[o].sent) + if (opts[o].slen != -1 && !opts[o].sent) fill_one(m, o, &offset); }
@@ -264,6 +269,9 @@ static void opt_set_dns_search(const struct ctx *c, size_t max_len) ".\xc0"); } } + + if (!opts[119].slen) + opts[119].slen = -1; }
/** @@ -313,6 +321,9 @@ int dhcp(const struct ctx *c, const struct pool *p)
offset += offsetof(struct msg, o);
+ for (i = 0; i < ARRAY_SIZE(opts); i++) + opts[i].clen = -1; + while (opt_off + 2 < opt_len) { const uint8_t *olen, *val; uint8_t *type; @@ -334,8 +345,9 @@ int dhcp(const struct ctx *c, const struct pool *p) if (opts[53].c[0] == DHCPDISCOVER) { info("DHCP: offer to discover"); opts[53].s[0] = DHCPOFFER; - } else if (opts[53].c[0] == DHCPREQUEST || !opts[53].clen) { - info("%s: ack to request", opts[53].clen ? "DHCP" : "BOOTP"); + } else if (opts[53].c[0] == DHCPREQUEST || opts[53].clen <= 0) { + info("%s: ack to request", /* DHCP needs a valid message type */ + (opts[53].clen <= 0) ? "DHCP" : "BOOTP"); opts[53].s[0] = DHCPACK; } else { return -1; @@ -374,6 +386,8 @@ int dhcp(const struct ctx *c, const struct pool *p) ((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 (!c->no_dhcp_dns_search) opt_set_dns_search(c, sizeof(m->o));
-- 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
I'm trying to speed up and simplify IP address acquisition in muvm.
Signed-off-by: Stefano Brivio
On Mon, Nov 25, 2024 at 04:28:11PM +0100, Stefano Brivio wrote:
I'm trying to speed up and simplify IP address acquisition in muvm.
Signed-off-by: Stefano Brivio
Reviewed-by: David Gibson
--- dhcp.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-)
diff --git a/dhcp.c b/dhcp.c index 57f69a5..90bb534 100644 --- a/dhcp.c +++ b/dhcp.c @@ -342,9 +342,16 @@ int dhcp(const struct ctx *c, const struct pool *p) opt_off += *olen + 2; }
+ opts[80].slen = -1; if (opts[53].c[0] == DHCPDISCOVER) { - info("DHCP: offer to discover"); - opts[53].s[0] = DHCPOFFER; + if (opts[80].clen == -1) { + info("DHCP: offer to discover"); + opts[53].s[0] = DHCPOFFER; + } else { + info("DHCP: ack to discover (Rapid Commit)"); + opts[53].s[0] = DHCPACK; + opts[80].slen = 0; + } } else if (opts[53].c[0] == DHCPREQUEST || opts[53].clen <= 0) { info("%s: ack to request", /* DHCP needs a valid message type */ (opts[53].clen <= 0) ? "DHCP" : "BOOTP");
-- 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
It's widely considered a legacy option nowadays, and I've haven't seen
clients setting it since Windows 95, but it's convenient for a minimal
DHCP client not using raw IP sockets such as what I'm playing with for
muvm.
Signed-off-by: Stefano Brivio
On Mon, Nov 25, 2024 at 04:28:12PM +0100, Stefano Brivio wrote:
It's widely considered a legacy option nowadays, and I've haven't seen clients setting it since Windows 95, but it's convenient for a minimal DHCP client not using raw IP sockets such as what I'm playing with for muvm.
Signed-off-by: Stefano Brivio
Reviewed-by: David Gibson
--- dhcp.c | 12 ++++++++++-- ip.h | 3 +++ 2 files changed, 13 insertions(+), 2 deletions(-)
diff --git a/dhcp.c b/dhcp.c index 90bb534..b3688ef 100644 --- a/dhcp.c +++ b/dhcp.c @@ -112,6 +112,8 @@ struct msg { uint32_t xid; uint16_t secs; uint16_t flags; +#define FLAG_BROADCAST htons_constant(0x8000) + uint32_t ciaddr; struct in_addr yiaddr; uint32_t siaddr; @@ -285,10 +287,10 @@ int dhcp(const struct ctx *c, const struct pool *p) { size_t mlen, dlen, offset = 0, opt_len, opt_off = 0; char macstr[ETH_ADDRSTRLEN]; + struct in_addr mask, dst; const struct ethhdr *eh; const struct iphdr *iph; const struct udphdr *uh; - struct in_addr mask; unsigned int i; struct msg *m;
@@ -400,7 +402,13 @@ int dhcp(const struct ctx *c, const struct pool *p) opt_set_dns_search(c, sizeof(m->o));
dlen = offsetof(struct msg, o) + fill(m); - tap_udp4_send(c, c->ip4.our_tap_addr, 67, c->ip4.addr, 68, m, dlen); + + if (m->flags & FLAG_BROADCAST) + dst = in4addr_broadcast; + else + dst = c->ip4.addr; + + tap_udp4_send(c, c->ip4.our_tap_addr, 67, dst, 68, m, dlen);
return 1; } diff --git a/ip.h b/ip.h index 0742612..1544dbf 100644 --- a/ip.h +++ b/ip.h @@ -101,4 +101,7 @@ static const struct in6_addr in6addr_ll_all_nodes = { }, };
+/* IPv4 Limited Broadcast (RFC 919, Section 7), 255.255.255.255 */ +static const struct in_addr in4addr_broadcast = { 0xffffffff }; + #endif /* IP_H */
-- 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
participants (2)
-
David Gibson
-
Stefano Brivio