Messages in this thread | | | Date | Tue, 23 Apr 2013 01:39:27 +0200 | From | Felix Becker <> | Subject | socket file descriptor a/m/c-timestamps broken in <= 3.8.8? |
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Hi,
I tried to figure out how old my TCP connections are and took a look at /proc/<pid>/fd/<socketfdnum> using 'ls -la' / 'stat'.
When I'm creating a new socket in my application, the time stamps returned by stat / ls -la are correct - as expected. After closing the socket, the fd isn't visible in /proc/<pid>/fd anymore - as expected. When creating a new socket a few minutes later (which gets the same number as the socket closed before), the newly created socket has the same time stamps (access / modify / change) as the old socket - I didn't expect this.
When using fstat() from <sys/stat.h> I'm getting 0 for a/m/c-time. Only in /proc/<pid>/fd/ i can see (the wrong) times.
I attached a test code for reproducing the issue. In my production environments i have new socket file descriptors which have timestamps indicating that they are many hours old.
Q1: is it a bug that fstat() returns 0-values for a/m/c-time?
Q2: is it a bug that a new socket, with the file descriptor number of an older socket which existed before, have the a/m/c-times of the old socket in /proc/<pid>/fd/?
Best regards
Felix
p.s. test setup is a normal x86_64 architecture (intel xeon).
======================================================================= // sockettest.c
#include <sys/socket.h> #include <time.h> #include <sys/stat.h> #include <sys/types.h> #include <sys/un.h> #include <stdlib.h> #include <stdio.h> #include <string.h> #include <unistd.h>
void print_socket_stats(int sfd){ struct stat socket_stats; fstat(sfd, &socket_stats); printf("Socket stats for socket %d\n", sfd); printf("socket stat: st_atime: %ld\n", socket_stats.st_atime); printf("socket stat: st_mtime: %ld\n", socket_stats.st_mtime); printf("socket stat: st_ctime: %ld\n", socket_stats.st_ctime); }
void print_with_time(const char* message){ time_t t; time(&t); printf("%s @ %s\n", message, ctime(&t));
}
int main(int argc, char *argv[]) {
int sfd;
printf("pid: %d\n", getpid());
print_with_time("Opening socket"); sfd = socket(AF_UNIX, SOCK_STREAM, 0); printf("opened socket: %d\n",sfd); print_socket_stats(sfd);
print_with_time("sleeping 30\n");
sleep(30);
printf("closing socket %d", sfd); close(sfd);
printf("closed socket: %d\n",sfd); print_with_time("sleeping 61 seconds");
sleep(61);
print_with_time("opening new socket"); sfd = socket(AF_UNIX, SOCK_STREAM, 0); printf("opened socket: %d\n",sfd); print_socket_stats(sfd); print_with_time("sleeping 999");
sleep(999); }
=======================================================================
./sockettest &
pid: 18267 Opening socket @ Mon Apr 22 23:05:37 2013
opened socket: 3 Socket stats for socket 3 socket stat: st_atime: 0 socket stat: st_mtime: 0 socket stat: st_ctime: 0 sleeping 30 @ Mon Apr 22 23:05:37 2013
>>> ls -la /proc/18267/fd/3 lrwx------ 1 becker becker 64 Apr 22 23:05 /proc/18267/fd/3 -> socket:[210268]
>>> stat /proc/18267/fd/3 File: `/proc/18267/fd/3' -> `socket:[210268]' Size: 64 Blocks: 0 IO Block: 1024 symbolic link Device: 3h/3d Inode: 52177 Links: 1 Access: (0700/lrwx------) Uid: ( 1001/ becker) Gid: ( 1001/ becker) Access: 2013-04-22 23:05:46.179813835 +0000 Modify: 2013-04-22 23:05:46.175813886 +0000 Change: 2013-04-22 23:05:46.175813886 +0000
closing socket 3 closed socket: 3
sleeping 61 seconds @ Mon Apr 22 23:06:07 2013
opening new socket @ Mon Apr 22 23:07:08 2013
opened socket: 3 Socket stats for socket 3 socket stat: st_atime: 0 socket stat: st_mtime: 0 socket stat: st_ctime: 0 sleeping 999 @ Mon Apr 22 23:07:08 2013
>>> ls -la /proc/18267/fd/3 lrwx------ 1 becker becker 64 Apr 22 23:05 /proc/18267/fd/3 -> socket:[210320]
>>> stat /proc/18267/fd/3
File: `/proc/18267/fd/3' -> `socket:[210320]' Size: 64 Blocks: 0 IO Block: 1024 symbolic link Device: 3h/3d Inode: 52177 Links: 1 Access: (0700/lrwx------) Uid: ( 1001/ becker) Gid: ( 1001/ becker) Access: 2013-04-22 23:05:46.179813835 +0000 Modify: 2013-04-22 23:05:46.175813886 +0000 Change: 2013-04-22 23:05:46.175813886 +0000
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