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resolved: don't downgrade feature level if we get RCODE on UDP level 

Retrying a transaction via TCP is a good approach for mitigating
packet loss. However, it's not a good away way to fix a bad RCODE if we
already downgraded to UDP level for it. Hence, don't do this.

This is a small tweak only, but shortens the time we spend on
downgrading when a specific domain continously returns a bad rcode.
This commit is contained in:
Lennart Poettering 2017-02-15 18:53:25 +01:00
parent 201d99584e
commit 7d581a6576
1 changed files with 8 additions and 4 deletions
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12
src/resolve/resolved-dns-transaction.c
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@ -911,9 +911,13 @@ void dns_transaction_process_reply(DnsTransaction *t, DnsPacket *p) {
/* Request failed, immediately try again with reduced features */
if (t->current_feature_level <= DNS_SERVER_FEATURE_LEVEL_WORST) {
/* This was already at the lowest possible feature level? If so, we can't downgrade
* this transaction anymore, hence let's process the response, and accept the rcode. */
if (t->current_feature_level <= DNS_SERVER_FEATURE_LEVEL_UDP) {
/* This was already at UDP feature level? If so, it doesn't make sense to downgrade
* this transaction anymore, hence let's process the response, and accept the
* rcode. Note that we don't retry on TCP, since that's a suitable way to mitigate
* packet loss, but is not going to give us better rcodes should we actually have
* managed to get them already at UDP level. */
log_debug("Server returned error: %s", dns_rcode_to_string(DNS_PACKET_RCODE(p)));
break;
}
@ -1136,7 +1140,7 @@ static int dns_transaction_emit_udp(DnsTransaction *t) {
return r;
if (t->current_feature_level < DNS_SERVER_FEATURE_LEVEL_UDP)
return -EAGAIN;
return -EAGAIN; /* Sorry, can't do UDP, try TCP! */
if (!dns_server_dnssec_supported(t->server) && dns_type_is_dnssec(t->key->type))
return -EOPNOTSUPP;