>From 32e06128dbc97ceb0d060c88ec8db204fa51be5c Mon Sep 17 00:00:00 2001
From: Stefan Zager <szager@google.com> Date: Thu, 18 Oct 2012 16:23:53 -0700 Subject: [PATCH] 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> --- http.c | 11 +++++++++++ 1 files changed, 11 insertions(+), 0 deletions(-)
diff --git a/http.c b/http.c index df9bb71..51eef02 100644 --- a/http.c +++ b/http.c @@ -631,6 +631,17 @@ 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); } }
-- 1.7.7.3
