Hello,
Bisected problems with setns() and /proc/net/sctp/snmp to this:
commit 1da4d377f943fe4194ffb9fb9c26cc58fad4dd24
Author: Alexey Dobriyan <adobriyan@xxxxxxxxx>
Date: Fri Apr 13 15:35:42 2018 -0700
proc: revalidate misc dentries
Reproduces for example with Fedora 5.9.10-100.fc32.x86_64, so 1fde6f21d90f
("proc: fix /proc/net/* after setns(2)") does not seem to cover
/proc/net/sctp/snmp
Reproducer attached, that does open+read+close of /proc/net/sctp/snmp before
and after setns() syscall. The second open+read+close of /proc/net/sctp/snmp
incorrectly produces results for the default namespace, not the target
namespace.
Example, create netns and do some sctp:
# ./iperf-netns
+ modprobe sctp
+ ip netns add test
+ ip netns exec test ip link set lo up
+ ip netns exec test iperf3 -s -1
-----------------------------------------------------------
Server listening on 5201
-----------------------------------------------------------
+ ip netns exec test iperf3 -c 127.0.0.1 --sctp --bitrate 50M --time 4
Connecting to host 127.0.0.1, port 5201
Accepted connection from 127.0.0.1, port 50696
[ 5] local 127.0.0.1 port 54735 connected to 127.0.0.1 port 5201
[ 5] local 127.0.0.1 port 5201 connected to 127.0.0.1 port 54735
[ ID] Interval Transfer Bitrate
[ ID] Interval Transfer Bitrate
[ 5] 0.00-1.00 sec 6.00 MBytes 50.3 Mbits/sec
[ 5] 0.00-1.00 sec 6.00 MBytes 50.3 Mbits/sec
[ 5] 1.00-2.00 sec 5.94 MBytes 49.8 Mbits/sec
[ 5] 1.00-2.00 sec 5.94 MBytes 49.8 Mbits/sec
[ 5] 2.00-3.00 sec 6.00 MBytes 50.3 Mbits/sec
[ 5] 2.00-3.00 sec 6.00 MBytes 50.3 Mbits/sec
[ 5] 3.00-4.00 sec 5.94 MBytes 49.8 Mbits/sec
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval Transfer Bitrate
[ 5] 0.00-4.00 sec 23.9 MBytes 50.1
Mbits/sec receiver
[ 5] 3.00-4.00 sec 5.94 MBytes 49.8 Mbits/sec
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval Transfer Bitrate
[ 5] 0.00-4.00 sec 23.9 MBytes 50.1 Mbits/sec
[ 5] 0.00-4.00 sec 23.9 MBytes 50.1
iperf Done.
+ cat /proc/net/sctp/snmp
SctpCurrEstab 0
SctpActiveEstabs 0
SctpPassiveEstabs 0
SctpAborteds 0
SctpShutdowns 0
SctpOutOfBlues 0
SctpChecksumErrors 0
[...]
+ ip netns exec test cat /proc/net/sctp/snmp
SctpCurrEstab 0
SctpActiveEstabs 2
SctpPassiveEstabs 2
SctpAborteds 0
SctpShutdowns 4
SctpOutOfBlues 0
SctpChecksumErrors 0
SctpOutCtrlChunks 1544
SctpOutOrderChunks 1530
[...]
+ wait
But now we see all zeroes in /proc/net/sctp/snmp with the reproducer:
$ gcc repro.c -o repro
# ./repro
/proc/net/sctp/snmp [pid: 175998]
SctpCurrEstab 0
SctpActiveEstabs 0
SctpPassiveEstabs 0
SctpAborteds 0
SctpShutdowns 0
[...]
setns(/run/netns/test) ...
/proc/net/sctp/snmp [pid: 175998]
SctpCurrEstab 0
SctpActiveEstabs 0
SctpPassiveEstabs 0
SctpAborteds 0
SctpShutdowns 0
SctpOutOfBlues 0
[...]
-Tommi
#define _GNU_SOURCE
#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <sched.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
void slurp(const char *fn)
{
char buf[8192];
ssize_t r;
int fd;
printf("%s [pid: %d]\n", fn, getpid()); fflush(stdout);
fd = open(fn, O_RDONLY);
if (fd < 0) { perror("open"); exit(1); }
r = read(fd, buf, sizeof(buf)-1);
if (r < 0) { perror("read"); exit(1); }
buf[r] = 0;
puts(buf); fflush(stdout);
if (close(fd) < 0) { perror("close"); exit(1); }
}
void newnet(const char *ns)
{
int fd;
fd = open(ns, O_RDONLY);
if (fd < 0) { perror("open"); exit(1); }
if (setns(fd, CLONE_NEWNET) < 0) { perror("setns"); exit(1); }
if (close(fd) < 0) { perror("close"); exit(1); }
}
int main(int argc, char **argv)
{
const char *ns = "/run/netns/test";
const char *fn = "/proc/net/sctp/snmp";
int d = 1;
// Optional args: /run/netns/... /proc/net/... n
if (argc >= 2) ns = argv[1];
if (argc >= 3) fn = argv[2];
if (argc >= 4 && argv[3][0] == 'n') d = 0;
if (d) slurp(fn);
printf("setns(%s) ...\n", ns); fflush(stdout);
newnet(ns);
slurp(fn);
}
Attachment:
iperf-netns
Description: iperf-netns
