emo/ndhc
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

Tolerate DHCP ACKs in REQUESTING state that don't match the serverid.

Browse Source 
Some networks have multiple DHCP servers that don't respect the
serverid that is specified in DHCPREQUESTs.

Instead we simply check to see that the yiaddr matches.

While we're at it, ignore DHCP NAK during REQUESTING state.  It
doesn't really make sense.  Instead we should just wait for
timeout.
This commit is contained in:
Nicholas J. Kain 2015-02-18 06:52:59 -05:00
parent f28495a58b
commit 29da5d21a4
1 changed files with 69 additions and 41 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

110
src/state.c
View File

@ -216,41 +216,47 @@ static int validate_serverid(struct client_state_t cs[static 1],
svrbuf, sizeof svrbuf);
log_line("%s: Received %s with an unexpected server id: %s. Ignoring it.",
client_config.interface, typemsg, svrbuf);
return 1; // XXX! HACK! Change back to 0!
return 0;
}
return 1;
}
static int an_packet(struct client_state_t cs[static 1],
struct dhcpmsg packet[static 1], uint8_t msgtype,
uint32_t srcaddr, bool is_requesting)
static void get_leasetime(struct client_state_t cs[static 1],
struct dhcpmsg packet[static 1])
{
cs->lease = get_option_leasetime(packet);
cs->leaseStartTime = curms();
if (!cs->lease) {
log_line("%s: No lease time received; assuming 1h.",
client_config.interface);
cs->lease = 60 * 60;
} else {
if (cs->lease < 60) {
log_warning("Server sent lease of <1m. Forcing lease to 1m.",
client_config.interface);
cs->lease = 60;
}
}
// Always use RFC2131 'default' values. It's not worth validating
// the remote server values, if they even exist, for sanity.
cs->renewTime = cs->lease >> 1;
cs->rebindTime = (cs->lease >> 3) * 0x7; // * 0.875
cs->dhcp_wake_ts = cs->leaseStartTime + cs->renewTime * 1000;
}
static int extend_packet(struct client_state_t cs[static 1],
struct dhcpmsg packet[static 1], uint8_t msgtype,
uint32_t srcaddr)
{
(void)srcaddr;
if (msgtype == DHCPACK) {
if (!validate_serverid(cs, packet, "a DHCP ACK"))
return ANP_IGNORE;
cs->lease = get_option_leasetime(packet);
cs->leaseStartTime = curms();
if (!cs->lease) {
log_line("%s: No lease time received; assuming 1h.",
client_config.interface);
cs->lease = 60 * 60;
} else {
if (cs->lease < 60) {
log_warning("Server sent lease of <1m. Forcing lease to 1m.",
client_config.interface);
cs->lease = 60;
}
}
// Always use RFC2131 'default' values. It's not worth validating
// the remote server values, if they even exist, for sanity.
cs->renewTime = cs->lease >> 1;
cs->rebindTime = (cs->lease >> 3) * 0x7; // * 0.875
cs->dhcp_wake_ts = cs->leaseStartTime + cs->renewTime * 1000;
get_leasetime(cs, packet);
// Only check if we are either in the REQUESTING state, or if we
// have received a lease with a different IP than what we had before.
if (is_requesting || memcmp(&packet->yiaddr, &cs->clientAddr, 4)) {
if (memcmp(&packet->yiaddr, &cs->clientAddr, 4)) {
char clibuf[INET_ADDRSTRLEN];
inet_ntop(AF_INET, &(struct in_addr){.s_addr=cs->clientAddr},
clibuf, sizeof clibuf);
@ -276,14 +282,11 @@ static int an_packet(struct client_state_t cs[static 1],
return ANP_IGNORE;
}
// XXX: This should also handle the REQUESTING part of an_packet and
// be used during REQUESTING; that will allow ndhc to track multiple
// DHCPOFFERs.
static int selecting_packet(struct client_state_t cs[static 1],
struct dhcpmsg packet[static 1], uint8_t msgtype,
uint32_t srcaddr)
uint32_t srcaddr, bool is_requesting)
{
if (msgtype == DHCPOFFER) {
if (!is_requesting && msgtype == DHCPOFFER) {
int found;
uint32_t sid = get_option_serverid(packet, &found);
if (!found) {
@ -294,8 +297,8 @@ static int selecting_packet(struct client_state_t cs[static 1],
char clibuf[INET_ADDRSTRLEN];
char svrbuf[INET_ADDRSTRLEN];
char srcbuf[INET_ADDRSTRLEN];
cs->serverAddr = sid;
cs->clientAddr = packet->yiaddr;
cs->serverAddr = sid;
cs->srcAddr = srcaddr;
cs->dhcp_wake_ts = curms();
cs->num_dhcp_requests = 0;
@ -308,6 +311,38 @@ static int selecting_packet(struct client_state_t cs[static 1],
log_line("%s: Received IP offer: %s from server %s via %s.",
client_config.interface, clibuf, svrbuf, srcbuf);
return ANP_SUCCESS;
} else if (is_requesting && msgtype == DHCPACK) {
// Don't validate the server id. Instead validate that the
// yiaddr matches. Some networks have multiple servers
// that don't respect the serverid that was specified in
// our DHCPREQUEST.
if (!memcmp(&packet->yiaddr, &cs->clientAddr, 4)) {
char clibuf[INET_ADDRSTRLEN];
char svrbuf[INET_ADDRSTRLEN];
char srcbuf[INET_ADDRSTRLEN];
int found;
uint32_t sid = get_option_serverid(packet, &found);
if (!found) {
log_line("%s: Invalid offer received: it didn't have a server id.",
client_config.interface);
return ANP_IGNORE;
}
if (cs->serverAddr != sid) {
cs->serverAddr = sid;
cs->srcAddr = srcaddr;
}
get_leasetime(cs, packet);
inet_ntop(AF_INET, &(struct in_addr){.s_addr=cs->clientAddr},
clibuf, sizeof clibuf);
inet_ntop(AF_INET, &(struct in_addr){.s_addr=cs->serverAddr},
svrbuf, sizeof svrbuf);
inet_ntop(AF_INET, &(struct in_addr){.s_addr=cs->srcAddr},
srcbuf, sizeof srcbuf);
log_line("%s: Received ACK: %s from server %s via %s. Validating...",
client_config.interface, clibuf, svrbuf, srcbuf);
return ANP_CHECK_IP;
}
}
return ANP_IGNORE;
}
@ -429,7 +464,7 @@ reinit:
int ret = COR_SUCCESS;
if (sev_dhcp) {
int r = selecting_packet(cs, dhcp_packet, dhcp_msgtype,
dhcp_srcaddr);
dhcp_srcaddr, false);
if (r == ANP_SUCCESS) {
// Send a request packet to the answering DHCP server.
sev_dhcp = false;
@ -452,16 +487,9 @@ reinit:
skip_to_requesting:
ret = COR_SUCCESS;
if (sev_dhcp) {
int r = an_packet(cs, dhcp_packet, dhcp_msgtype, dhcp_srcaddr,
true);
int r = selecting_packet(cs, dhcp_packet, dhcp_msgtype,
dhcp_srcaddr, true);
if (r == ANP_IGNORE) {
} else if (r == ANP_FAIL) {
ret = COR_ERROR;
scrReturn(ret);
continue;
} else if (r == ANP_REJECTED) {
sev_dhcp = false;
goto reinit;
} else if (r == ANP_CHECK_IP) {
if (arp_check(cs, dhcp_packet) < 0) {
log_warning("%s: Failed to make arp socket. Searching for new lease...",
@ -550,8 +578,7 @@ skip_to_requesting:
for (;;) {
int ret = COR_SUCCESS;
if (sev_dhcp && is_renewing(cs, nowts)) {
int r = an_packet(cs, dhcp_packet, dhcp_msgtype, dhcp_srcaddr,
false);
int r = extend_packet(cs, dhcp_packet, dhcp_msgtype, dhcp_srcaddr);
if (r == ANP_SUCCESS || r == ANP_IGNORE) {
} else if (r == ANP_FAIL) {
ret = COR_ERROR;
@ -651,6 +678,7 @@ skip_to_requesting:
int r = ifup_action(cs);
if (r == IFUP_REVALIDATE) {
} else if (r == IFUP_NEWLEASE) {
// XXX: Deconfigure the interface. The network has changed.
if (reinit_selecting(cs, 0) < 0) {
ret = COR_ERROR;
scrReturn(ret);