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Diffstat (limited to 'dhcp.c')
-rw-r--r--dhcp.c163
1 files changed, 125 insertions, 38 deletions
diff --git a/dhcp.c b/dhcp.c
index ff4834a..b0de04b 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 {
@@ -63,11 +63,21 @@ static struct opt opts[255];
#define OPT_MIN 60 /* RFC 951 */
+/* Total option size (excluding end option) is 576 (RFC 2131), minus
+ * offset of options (268), minus end option (1).
+ */
+#define OPT_MAX 307
+
/**
* dhcp_init() - Initialise DHCP options
*/
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,
@@ -107,6 +117,8 @@ 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;
@@ -115,7 +127,7 @@ struct msg {
uint8_t sname[64];
uint8_t file[128];
uint32_t magic;
- uint8_t o[308];
+ uint8_t o[OPT_MAX + 1 /* End option */ ];
} __attribute__((__packed__));
/**
@@ -123,15 +135,28 @@ struct msg {
* @m: Message to fill
* @o: Option number
* @offset: Current offset within options field, updated on insertion
+ *
+ * Return: false if m has space to write the option, true otherwise
*/
-static void fill_one(struct msg *m, int o, int *offset)
+static bool fill_one(struct msg *m, 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)
+ return true;
+
m->o[*offset] = o;
- m->o[*offset + 1] = opts[o].slen;
- memcpy(&m->o[*offset + 2], opts[o].s, opts[o].slen);
+ m->o[*offset + 1] = slen;
+
+ /* Move to option */
+ *offset += 2;
+
+ memcpy(&m->o[*offset], opts[o].s, slen);
opts[o].sent = 1;
- *offset += 2 + opts[o].slen;
+ *offset += slen;
+ return false;
}
/**
@@ -144,9 +169,6 @@ static int fill(struct msg *m)
{
int i, o, offset = 0;
- m->op = BOOTREPLY;
- m->secs = 0;
-
for (o = 0; o < 255; o++)
opts[o].sent = 0;
@@ -154,22 +176,24 @@ 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))
- fill_one(m, 53, &offset);
+ if (opts[55].clen > 0 && !memchr(opts[55].c, 53, opts[55].clen))
+ if (fill_one(m, 53, &offset))
+ debug("DHCP: skipping option 53");
for (i = 0; i < opts[55].clen; i++) {
o = opts[55].c[i];
- if (opts[o].slen)
- fill_one(m, o, &offset);
+ if (opts[o].slen != -1)
+ if (fill_one(m, o, &offset))
+ debug("DHCP: skipping option %i", o);
}
for (o = 0; o < 255; o++) {
- if (opts[o].slen && !opts[o].sent)
- fill_one(m, o, &offset);
+ if (opts[o].slen != -1 && !opts[o].sent)
+ if (fill_one(m, o, &offset))
+ debug("DHCP: skipping option %i", o);
}
m->o[offset++] = 255;
- m->o[offset++] = 0;
if (offset < OPT_MIN) {
memset(&m->o[offset], 0, OPT_MIN - offset);
@@ -264,6 +288,9 @@ static void opt_set_dns_search(const struct ctx *c, size_t max_len)
".\xc0");
}
}
+
+ if (!opts[119].slen)
+ opts[119].slen = -1;
}
/**
@@ -275,13 +302,15 @@ static void opt_set_dns_search(const struct ctx *c, size_t max_len)
*/
int dhcp(const struct ctx *c, const struct pool *p)
{
- size_t mlen, len, offset = 0, opt_len, opt_off = 0;
+ 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;
+ struct msg const *m;
+ struct msg reply;
unsigned int i;
- struct msg *m;
eh = packet_get(p, 0, offset, sizeof(*eh), NULL);
offset += sizeof(*eh);
@@ -310,8 +339,27 @@ int dhcp(const struct ctx *c, const struct pool *p)
m->op != BOOTREQUEST)
return -1;
+ reply.op = BOOTREPLY;
+ reply.htype = m->htype;
+ reply.hlen = m->hlen;
+ reply.hops = 0;
+ reply.xid = m->xid;
+ reply.secs = 0;
+ reply.flags = m->flags;
+ reply.ciaddr = m->ciaddr;
+ reply.yiaddr = c->ip4.addr;
+ reply.siaddr = 0;
+ reply.giaddr = m->giaddr;
+ memcpy(&reply.chaddr, m->chaddr, sizeof(reply.chaddr));
+ memset(&reply.sname, 0, sizeof(reply.sname));
+ memset(&reply.file, 0, sizeof(reply.file));
+ reply.magic = m->magic;
+
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;
@@ -330,39 +378,46 @@ int dhcp(const struct ctx *c, const struct pool *p)
opt_off += *olen + 2;
}
- 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");
+ opts[80].slen = -1;
+ if (opts[53].clen > 0 && opts[53].c[0] == DHCPDISCOVER) {
+ 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].clen <= 0 || opts[53].c[0] == DHCPREQUEST) {
+ info("%s: ack to request", /* DHCP needs a valid message type */
+ (opts[53].clen <= 0) ? "BOOTP" : "DHCP");
opts[53].s[0] = DHCPACK;
} else {
return -1;
}
- info(" from %02x:%02x:%02x:%02x:%02x:%02x",
- m->chaddr[0], m->chaddr[1], m->chaddr[2],
- m->chaddr[3], m->chaddr[4], m->chaddr[5]);
+ info(" from %s", eth_ntop(m->chaddr, macstr, sizeof(macstr)));
- m->yiaddr = c->ip4.addr;
mask.s_addr = htonl(0xffffffff << (32 - c->ip4.prefix_len));
- memcpy(opts[1].s, &mask, sizeof(mask));
- memcpy(opts[3].s, &c->ip4.gw, sizeof(c->ip4.gw));
- memcpy(opts[54].s, &c->ip4.gw, sizeof(c->ip4.gw));
+ 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 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)
- != (c->ip4.gw.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;
opts[121].s[0] = 32;
- memcpy(opts[121].s + 1, &c->ip4.gw, sizeof(c->ip4.gw));
- memcpy(opts[121].s + 10, &c->ip4.gw, sizeof(c->ip4.gw));
+ memcpy(opts[121].s + 1,
+ &c->ip4.guest_gw, sizeof(c->ip4.guest_gw));
+ memcpy(opts[121].s + 10,
+ &c->ip4.guest_gw, sizeof(c->ip4.guest_gw));
}
- if (c->mtu != -1) {
+ if (c->mtu) {
opts[26].slen = 2;
opts[26].s[0] = c->mtu / 256;
opts[26].s[1] = c->mtu % 256;
@@ -373,12 +428,44 @@ 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;
+
+ opt_len = strlen(c->hostname);
+ if (opt_len > 0) {
+ opts[12].slen = opt_len;
+ memcpy(opts[12].s, &c->hostname, opt_len);
+ }
+
+ opt_len = strlen(c->fqdn);
+ if (opt_len > 0) {
+ opt_len += 3 /* flags */
+ + 2; /* Length byte for first label, and terminator */
+
+ if (sizeof(opts[81].s) >= opt_len) {
+ opts[81].s[0] = 0x4; /* flags (E) */
+ opts[81].s[1] = 0xff; /* RCODE1 */
+ opts[81].s[2] = 0xff; /* RCODE2 */
+
+ encode_domain_name((char *)opts[81].s + 3, c->fqdn);
+
+ opts[81].slen = opt_len;
+ } else {
+ debug("DHCP: client FQDN option doesn't fit, skipping");
+ }
+ }
if (!c->no_dhcp_dns_search)
opt_set_dns_search(c, sizeof(m->o));
- len = offsetof(struct msg, o) + fill(m);
- tap_udp4_send(c, c->ip4.gw, 67, c->ip4.addr, 68, m, len);
+ dlen = offsetof(struct msg, o) + fill(&reply);
+
+ 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, &reply, dlen);
return 1;
}
generated by cgit v1.2.3 (git 2.25.1) at 2025-07-04 00:47:53 +0000