@matheusbsbs / matheus-bagliano / commits / 7202b81ffc

Fix potential hang in https handshake

It has been observed that curl_multi_timeout may return a very long timeout value (e.g., 294 seconds and some usec) just before curl_multi_fdset returns no file descriptors for reading. The upshot is that select() will hang for a long time -- long enough for an https handshake to be dropped. The observed behavior is that the git command will hang at the terminal and never transfer any data. This patch is a workaround for a probable bug in libcurl. The bug only seems to manifest around a very specific set of circumstances: - curl version (from curl/curlver.h): #define LIBCURL_VERSION_NUM 0x071307 - git-remote-https running on an ubuntu-lucid VM. - Connecting through squid proxy running on another VM. Interestingly, the problem doesn't manifest if a host connects through squid proxy running on localhost; only if the proxy is on a separate VM (not sure if the squid host needs to be on a separate physical machine). That would seem to suggest that this issue is timing-sensitive. This patch is more or less in line with a recommendation in the curl docs about how to behave when curl_multi_fdset doesn't return and file descriptors: http://curl.haxx.se/libcurl/c/curl_multi_fdset.html Signed-off-by: Stefan Zager <szager@google.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>

Stefan Zager committed Oct 19, 2012 at 14:04 UTC 7202b81ffccf89605ce2726ff9d63202b5f1da7f

1 file changed +12

http.c

+12

@@ -631,6 +631,18 @@ void run_active_slot(struct active_request_slot *slot)

631 FD_ZERO(&excfds);

632 curl_multi_fdset(curlm, &readfds, &writefds, &excfds, &max_fd);

633

634 + /*

635 + * It can happen that curl_multi_timeout returns a pathologically

636 + * long timeout when curl_multi_fdset returns no file descriptors

637 + * to read. See commit message for more details.

638 + */

639 + if (max_fd < 0 &&

640 + (select_timeout.tv_sec > 0 ||

641 + select_timeout.tv_usec > 50000)) {

642 + select_timeout.tv_sec = 0;

643 + select_timeout.tv_usec = 50000;

644 + }

645 +

646 select(max_fd+1, &readfds, &writefds, &excfds, &select_timeout);

647 }

648 }