2 Commits

Author	SHA1	Message	Date
Yu Watanabe	16a6bc5a7a	resolve: dedup entries in /etc/hosts ... This improves the performance of parsing the file and reduces memory pressure. Running 'fuzz-etc-hosts timeout-strv' with valgrind, Before: total heap usage: 321,020 allocs, 321,020 frees, 15,820,387,193 bytes allocated real 0m23.531s user 0m21.458s sys 0m1.961s After: total heap usage: 112,408 allocs, 112,408 frees, 7,297,480 bytes allocated real 0m8.664s user 0m8.545s sys 0m0.065s Hopefully fixes oss-fuzz#47708 (https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=47708).	2022-12-13 20:37:48 +09:00
Zbigniew Jędrzejewski-Szmek	eb164c51ea	resolved: use strv_extend_with_size() to avoid slow parsing of /etc/hosts ... https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=43942 is a simple case where a repeated entry generates a timeout. I didn't import that case, but generated a simpler one by hand. $ time build/fuzz-etc-hosts test/fuzz/fuzz-etc-hosts/timeout-many-entries test/fuzz/fuzz-etc-hosts/timeout-many-entries... ok build/fuzz-etc-hosts test/fuzz/fuzz-etc-hosts/timeout-many-entries 3.17s (old) ↓ build/fuzz-etc-hosts test/fuzz/fuzz-etc-hosts/timeout-many-entries 0.11s (new) I considered simply disallowing too many aliases. E.g. microsoft appearently sometimes ignores entries after the ninth [1], and other systems set stringent limits [2,3], but the recommended way to get around that is to simply use more lines (as is done in the sample), so this wouldn't change anything. Even if we cannot put all those names in a reply packet, the resolution from the alias to the address should work. I think cases where people define lots and lots of aliases through some programmatic interface is realistic, for example for a blocklist, and such a file shouldn't bring resolved down to its knees. [1] https://superuser.com/questions/932112/is-there-a-maximum-number-of-hostname-aliases-per-line-in-a-windows-hosts-file [2] https://library.netapp.com/ecmdocs/ECMP1516135/html/GUID-C6F3B6D1-232D-44BB-A76C-3304C19607A3.html [3] https://www.ibm.com/docs/en/zos/2.1.0?topic=optional-creating-etchosts	2022-05-20 15:18:28 +02:00