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authorStefan Zager <szager@google.com>2012-10-19 14:04:20 -0700
committerJunio C Hamano <gitster@pobox.com>2012-10-19 14:15:17 -0700
commit7202b81ffccf89605ce2726ff9d63202b5f1da7f (patch)
tree3078366221d7e05daa7dd3f140f85f2600668bbc /http.c
parent7e2010537e96d0a1144520222f20ba1dc3d61441 (diff)
downloadgit-7202b81ffccf89605ce2726ff9d63202b5f1da7f.tar.gz
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>
Diffstat (limited to 'http.c')
-rw-r--r--http.c12
1 files changed, 12 insertions, 0 deletions
diff --git a/http.c b/http.c
index df9bb71086..f9a9de1416 100644
--- a/http.c
+++ b/http.c
@@ -631,6 +631,18 @@ void run_active_slot(struct active_request_slot *slot)
FD_ZERO(&excfds);
curl_multi_fdset(curlm, &readfds, &writefds, &excfds, &max_fd);
+ /*
+ * It can happen that curl_multi_timeout returns a pathologically
+ * long timeout when curl_multi_fdset returns no file descriptors
+ * to read. See commit message for more details.
+ */
+ if (max_fd < 0 &&
+ (select_timeout.tv_sec > 0 ||
+ select_timeout.tv_usec > 50000)) {
+ select_timeout.tv_sec = 0;
+ select_timeout.tv_usec = 50000;
+ }
+
select(max_fd+1, &readfds, &writefds, &excfds, &select_timeout);
}
}