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dhcp: Use -1 as "missing option" length instead of 0

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We want to add support for option 80 (Rapid Commit, RFC 4039), whose
length is 0.

Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
This commit is contained in:
Stefano Brivio 2024-11-15 18:13:17 +01:00
parent 14b84a7f07
commit d6e9e2486f
1 changed files with 22 additions and 8 deletions
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30
dhcp.c
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@ -36,9 +36,9 @@
/** /**
* struct opt - DHCP option * struct opt - DHCP option
* @sent: Convenience flag, set while filling replies * @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 * @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 * @c: Option payload from client
*/ */
struct opt { struct opt {
@ -68,6 +68,11 @@ static struct opt opts[255];
*/ */
void dhcp_init(void) 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[1] = (struct opt) { 0, 4, { 0 }, 0, { 0 }, }; /* Mask */
opts[3] = (struct opt) { 0, 4, { 0 }, 0, { 0 }, }; /* Router */ opts[3] = (struct opt) { 0, 4, { 0 }, 0, { 0 }, }; /* Router */
opts[51] = (struct opt) { 0, 4, { 0xff, 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. * option 53 at the beginning of the list.
* Put it there explicitly, unless requested via option 55. * 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); fill_one(m, 53, &offset);
for (i = 0; i < opts[55].clen; i++) { for (i = 0; i < opts[55].clen; i++) {
o = opts[55].c[i]; o = opts[55].c[i];
if (opts[o].slen) if (opts[o].slen != -1)
fill_one(m, o, &offset); fill_one(m, o, &offset);
} }
for (o = 0; o < 255; o++) { 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); fill_one(m, o, &offset);
} }
@ -264,6 +269,9 @@ static void opt_set_dns_search(const struct ctx *c, size_t max_len)
".\xc0"); ".\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); offset += offsetof(struct msg, o);
for (i = 0; i < ARRAY_SIZE(opts); i++)
opts[i].clen = -1;
while (opt_off + 2 < opt_len) { while (opt_off + 2 < opt_len) {
const uint8_t *olen, *val; const uint8_t *olen, *val;
uint8_t *type; uint8_t *type;
@ -331,11 +342,12 @@ int dhcp(const struct ctx *c, const struct pool *p)
opt_off += *olen + 2; opt_off += *olen + 2;
} }
if (opts[53].c[0] == DHCPDISCOVER) { if (opts[53].clen > 0 && opts[53].c[0] == DHCPDISCOVER) {
info("DHCP: offer to discover"); info("DHCP: offer to discover");
opts[53].s[0] = DHCPOFFER; opts[53].s[0] = DHCPOFFER;
} else if (opts[53].c[0] == DHCPREQUEST || !opts[53].clen) { } else if (opts[53].clen <= 0 || opts[53].c[0] == DHCPREQUEST) {
info("%s: ack to request", opts[53].clen ? "DHCP" : "BOOTP"); info("%s: ack to request", /* DHCP needs a valid message type */
(opts[53].clen <= 0) ? "BOOTP" : "DHCP");
opts[53].s[0] = DHCPACK; opts[53].s[0] = DHCPACK;
} else { } else {
return -1; 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]; ((struct in_addr *)opts[6].s)[i] = c->ip4.dns[i];
opts[6].slen += sizeof(uint32_t); opts[6].slen += sizeof(uint32_t);
} }
if (!opts[6].slen)
opts[6].slen = -1;
if (!c->no_dhcp_dns_search) if (!c->no_dhcp_dns_search)
opt_set_dns_search(c, sizeof(m->o)); opt_set_dns_search(c, sizeof(m->o));