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Fix bug in 6860cf932b

Browse Source 
The optimisation based on the assumption that
"try now points to the last domain that sorts before the query"
fails in the specific edge case that the query sorts before
_any_ of the server domains. Handle this case.

Thanks to Xingcong Li for finding a test case for this bug.
This commit is contained in:
Simon Kelley
2021-06-20 22:57:54 +01:00
parent d0ae3f5a4d
commit a0a3b8ad3e
1 changed files with 26 additions and 22 deletions
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46
src/domain-match.c
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@@ -133,7 +133,32 @@ int lookup_domain(char *qdomain, int flags, int *lowout, int *highout)
else
{
if (low == try)
{
/* try now points to the last domain that sorts before the query, so
we know that a substring of the query shorter than it is required to match, so
find the largest domain that's shorter than try. Note that just going to
try+1 is not optimal, consider searching bbb in (aaa,ccc,bb). try will point
to aaa, since ccc sorts after bbb, but the first domain that has a chance to
match is bb. So find the length of the first domain later than try which is
is shorter than it.
There's a nasty edge case when qdomain sorts before _any_ of the
server domains, where try _doesn't point_ to the last domain that sorts
before the query, since no such domain exists. In that case, the loop
exits via the rc < 0 && high == try path above and this code is
not executed. */
ssize_t len, old = daemon->serverarray[try]->domain_len;
while (++try != daemon->serverarraysz)
{
if (old != (len = daemon->serverarray[try]->domain_len))
{
/* crop_query must be at least one always. */
if (qlen != len)
crop_query = qlen - len;
break;
}
}
break;
}
low = try;
}
};
@@ -153,27 +178,6 @@ int lookup_domain(char *qdomain, int flags, int *lowout, int *highout)
break;
}
}
else
{
/* try now points to the last domain that sorts before the query, so
we know that a substring of the query shorter than it is required to match, so
find the largest domain that's shorter than try. Note that just going to
try+1 is not optimal, consider searching bbb in (aaa,ccc,bb). try will point
to aaa, since ccc sorts after bbb, but the first domain that has a chance to
match is dd. So find the length of the first domain later than try which is
is shorter than it. */
ssize_t len, old = daemon->serverarray[try]->domain_len;
while (++try != daemon->serverarraysz)
{
if (old != (len = daemon->serverarray[try]->domain_len))
{
/* crop_query must be at least one always. */
if (qlen != len)
crop_query = qlen - len;
break;
}
}
}
qlen -= crop_query;
if (leading_dot)