[libvirt] lxc_controller: don't ignore failed "accept"

Initially I proposed a similar patch here: http://thread.gmane.org/gmane.comp.emulators.libvirt/20607 That thread languished, and Eric proposed a nearly identical patch: http://thread.gmane.org/gmane.comp.emulators.libvirt/21630 Here's a patch that should address the initial objection. Now, my only question is about which errno values to ignore. Obviously, EMFILE, EFAULT, etc. must not be ignored. I doubt EINTR and EBADF should be ignored, but haven't tried to prove the case. From: Jim Meyering <meyering(a)redhat.com&gt; Date: Thu, 20 May 2010 14:30:36 +0200 Subject: [PATCH] lxc_controller.c: don't ignore failed "accept" * src/lxc/lxc_controller.c (ignorable_epoll_accept_errno): New function. (lxcControllerMain): Handle a failed accept carefully: most errno values indicate legitimate failure and must be fatal. However, ignore a special case: that in which an incoming client quits between the poll() indicating its presence, and our accept() which is trying to process it. --- src/lxc/lxc_controller.c | 23 +++++++++++++++++++++++ 1 files changed, 23 insertions(+), 0 deletions(-) diff --git a/src/lxc/lxc_controller.c b/src/lxc/lxc_controller.c index 6b64372..75a45e9 100644 --- a/src/lxc/lxc_controller.c +++ b/src/lxc/lxc_controller.c @@ -269,6 +269,17 @@ typedef struct _lxcTtyForwardFd_t { int active; } lxcTtyForwardFd_t; +/* Return true if it is ok to ignore an accept-after-epoll syscall + that fails with the specified errno value. Else false. */ +static bool +ignorable_epoll_accept_errno(int erratum) +{ + return (errnum == EINVAL + || errnum == ECONNABORTED + || errnum == EAGAIN + || errnum == EWOULDBLOCK); +} + /** * lxcControllerMain * @monitor: server socket fd to accept client requests @@ -350,6 +361,18 @@ static int lxcControllerMain(int monitor, if (numEvents > 0) { if (epollEvent.data.fd == monitor) { int fd = accept(monitor, NULL, 0); + if (fd < 0) { + /* First reflex may be simply to declare accept failure + to be a fatal error. However, accept may fail when + a client quits between the above epoll_wait and here. + That case is not fatal, but rather to be expected, + if not common, so ignore it. */ + if (ignorable_epoll_accept_errno(errno)) + continue; + virReportSystemError(errno, "%s", + _("accept(monitor,...) failed")); + goto cleanup; + } if (client != -1) { /* Already connected, so kick new one out */ close(fd); continue; -- 1.7.1.262.g5ef3d