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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.
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@ -779,15 +779,40 @@ static int on_dns_packet(sd_event_source *s, int fd, uint32_t revents, void *use
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assert(t->scope);
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r = manager_recv(t->scope->manager, fd, DNS_PROTOCOL_DNS, &p);
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if (r <= 0)
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return r;
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if (ERRNO_IS_DISCONNECT(-r)) {
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usec_t usec;
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if (dns_packet_validate_reply(p) > 0 &&
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DNS_PACKET_ID(p) == t->id)
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dns_transaction_process_reply(t, p);
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else
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log_debug("Invalid DNS UDP packet, ignoring.");
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/* UDP connection failure get reported via ICMP and then are possible delivered to us on the next
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* recvmsg(). Treat this like a lost packet. */
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log_debug_errno(r, "Connection failure for DNS UDP packet, treating as lost packet: %m");
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assert_se(sd_event_now(t->scope->manager->event, clock_boottime_or_monotonic(), &usec) >= 0);
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dns_server_packet_lost(t->server, t->current_features, usec - t->start_usec);
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dns_transaction_retry(t);
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return 0;
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}
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if (r < 0) {
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dns_transaction_complete(t, DNS_TRANSACTION_RESOURCES);
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return 0;
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}
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r = dns_packet_validate_reply(p);
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if (r < 0) {
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log_debug_errno(r, "Received invalid DNS packet as response, ignoring: %m");
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return 0;
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}
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if (r == 0) {
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log_debug("Received inappropriate DNS packet as response, ignoring: %m");
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return 0;
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}
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if (DNS_PACKET_ID(p) != t->id) {
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log_debug("Received packet with incorrect transaction ID, ignoring: %m");
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return 0;
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}
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dns_transaction_process_reply(t, p);
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return 0;
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}
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