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Fix confusion in DNS retries and --strict-order.

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Behaviour to stop infinite loops when all servers return REFUSED
was wrongly activated on client retries, resulting in
incorrect REFUSED replies to client retries.

Thanks to Johannes Stezenbach for finding the problem.
This commit is contained in:
Simon Kelley
2021-09-27 22:37:02 +01:00
parent 47aefca5e4
commit 2561f9fe0e
1 changed files with 16 additions and 4 deletions
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16
src/forward.c
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@@ -173,7 +173,7 @@ static int forward_query(int udpfd, union mysockaddr *udpaddr,
unsigned int gotname = extract_request(header, plen, daemon->namebuff, NULL); unsigned int gotname = extract_request(header, plen, daemon->namebuff, NULL);
void *hash = hash_questions(header, plen, daemon->namebuff); void *hash = hash_questions(header, plen, daemon->namebuff);
unsigned char *oph = find_pseudoheader(header, plen, NULL, NULL, NULL, NULL); unsigned char *oph = find_pseudoheader(header, plen, NULL, NULL, NULL, NULL);
int old_src = 0; int old_src = 0, old_reply = 0;
int first, last, start = 0; int first, last, start = 0;
int subnet, cacheable, forwarded = 0; int subnet, cacheable, forwarded = 0;
size_t edns0_len; size_t edns0_len;
@@ -199,7 +199,10 @@ static int forward_query(int udpfd, union mysockaddr *udpaddr,
Similarly FREC_NO_CACHE is never set in flags, so a query which is Similarly FREC_NO_CACHE is never set in flags, so a query which is
contigent on a particular source address EDNS0 option will never be matched. */ contigent on a particular source address EDNS0 option will never be matched. */
if (forward) if (forward)
{
old_src = 1; old_src = 1;
old_reply = 1;
}
else if ((forward = lookup_frec_by_query(hash, fwd_flags, else if ((forward = lookup_frec_by_query(hash, fwd_flags,
FREC_CHECKING_DISABLED | FREC_AD_QUESTION | FREC_DO_QUESTION | FREC_CHECKING_DISABLED | FREC_AD_QUESTION | FREC_DO_QUESTION |
FREC_HAS_PHEADER | FREC_DNSKEY_QUERY | FREC_DS_QUERY | FREC_NO_CACHE))) FREC_HAS_PHEADER | FREC_DNSKEY_QUERY | FREC_DS_QUERY | FREC_NO_CACHE)))
@@ -376,9 +379,18 @@ static int forward_query(int udpfd, union mysockaddr *udpaddr,
/* In strict order mode, there must be a server later in the list /* In strict order mode, there must be a server later in the list
left to send to, otherwise without the forwardall mechanism, left to send to, otherwise without the forwardall mechanism,
code further on will cycle around the list forwever if they code further on will cycle around the list forwever if they
all return REFUSED. If at the last, give up. */ all return REFUSED. If at the last, give up.
Note that we can get here EITHER because a client retried,
or an upstream server returned REFUSED. The above only
applied in the later case. For client retries,
keep tyring the last server.. */
if (++start == last) if (++start == last)
{
if (old_reply)
goto reply; goto reply;
else
start--;
}
} }
} }
} }