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resolved: properly handle UDP ICMP errors as lost packets 

UDP ICMP errors are reported to us via recvmsg() when we read a reply. Handle this properly, and consider this a lost
packet, and retry the connection.

This also adds some additional logging for invalid incoming packets.
This commit is contained in:
Lennart Poettering 2016-01-08 02:38:00 +01:00
parent a1a3f73a57
commit 7e1851e3c6
1 changed files with 32 additions and 7 deletions
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39
src/resolve/resolved-dns-transaction.c
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@ -779,15 +779,40 @@ static int on_dns_packet(sd_event_source *s, int fd, uint32_t revents, void *use
assert(t->scope);
r = manager_recv(t->scope->manager, fd, DNS_PROTOCOL_DNS, &p);
if (r <= 0)
return r;
if (ERRNO_IS_DISCONNECT(-r)) {
usec_t usec;
if (dns_packet_validate_reply(p) > 0 &&
DNS_PACKET_ID(p) == t->id)
dns_transaction_process_reply(t, p);
else
log_debug("Invalid DNS UDP packet, ignoring.");
/* UDP connection failure get reported via ICMP and then are possible delivered to us on the next
* recvmsg(). Treat this like a lost packet. */
log_debug_errno(r, "Connection failure for DNS UDP packet, treating as lost packet: %m");
assert_se(sd_event_now(t->scope->manager->event, clock_boottime_or_monotonic(), &usec) >= 0);
dns_server_packet_lost(t->server, t->current_features, usec - t->start_usec);
dns_transaction_retry(t);
return 0;
}
if (r < 0) {
dns_transaction_complete(t, DNS_TRANSACTION_RESOURCES);
return 0;
}
r = dns_packet_validate_reply(p);
if (r < 0) {
log_debug_errno(r, "Received invalid DNS packet as response, ignoring: %m");
return 0;
}
if (r == 0) {
log_debug("Received inappropriate DNS packet as response, ignoring: %m");
return 0;
}
if (DNS_PACKET_ID(p) != t->id) {
log_debug("Received packet with incorrect transaction ID, ignoring: %m");
return 0;
}
dns_transaction_process_reply(t, p);
return 0;
}