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Handle truncated response UDP-to-TCP to downstream queries when validating.

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A relatively common situation is that the reply to a downstream query
will fit in a UDP packet when no DNSSEC RRs are present, but overflows
when the RRSIGS, NSEC ect are added. This extends the automatic
move from UDP to TCP to downstream queries which get truncated replies,
in the hope that once stripped of the DNSSEC RRs, the reply can be returned
via UDP, nwithout making the downstream retry with TCP.

If the downstream sets the DO bit, (ie it wants the DNSSEC RRs, then
this path is not taken, since the downstream will have to get a truncated
repsonse and retry to get a correct answer.
This commit is contained in:
Simon Kelley
2024-10-12 22:25:06 +01:00
parent 1c26ec2876
commit d15d371051
6 changed files with 193 additions and 88 deletions
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28
src/cache.c
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@@ -898,10 +898,16 @@ int cache_recv_insert(time_t now, int fd)
{
int status, uid, keycount, validatecount;
int *keycountp, *validatecountp;
size_t ret_len;
struct frec *forward;
if (!read_write(fd, (unsigned char *)&status, sizeof(status), 1))
return 0;
if (!read_write(fd, (unsigned char *)&ret_len, sizeof(ret_len), 1))
return 0;
if (!read_write(fd, (unsigned char *)daemon->packet, ret_len, 1))
return 0;
if (!read_write(fd, (unsigned char *)&forward, sizeof(forward), 1))
return 0;
if (!read_write(fd, (unsigned char *)&uid, sizeof(uid), 1))
@@ -923,10 +929,13 @@ int cache_recv_insert(time_t now, int fd)
/* repatriate the work counters from the child process. */
*keycountp = keycount;
*validatecountp = validatecount;
pop_and_retry_query(forward, status, now);
if (!forward->dependent)
return_reply(now, forward, (struct dns_header *)daemon->packet, ret_len, status);
else
pop_and_retry_query(forward, status, now);
}
return 1;
}
#endif
@@ -2281,12 +2290,21 @@ void log_query(unsigned int flags, char *name, union all_addr *addr, char *arg,
if (option_bool(OPT_EXTRALOG))
{
int display_id = daemon->log_display_id;
char *proto = "";
if (option_bool(OPT_LOG_PROTO))
proto = (display_id < 0) ? "TCP " : "UDP ";
if (display_id < 0)
display_id = -display_id;
if (flags & F_NOEXTRA)
my_syslog(LOG_INFO, "%u %s %s%s%s %s%s", daemon->log_display_id, source, name, gap, verb, dest, extra);
my_syslog(LOG_INFO, "%s%u %s %s%s%s %s%s", proto, display_id, source, name, gap, verb, dest, extra);
else
{
int port = prettyprint_addr(daemon->log_source_addr, daemon->addrbuff2);
my_syslog(LOG_INFO, "%u %s/%u %s %s%s%s %s%s", daemon->log_display_id, daemon->addrbuff2, port, source, name, gap, verb, dest, extra);
my_syslog(LOG_INFO, "%s%u %s/%u %s %s%s%s %s%s", proto, display_id, daemon->addrbuff2, port, source, name, gap, verb, dest, extra);
}
}
else