procfs has data consistency issues when reading /proc/net/tcp #576
Description
Line 28 in ff0ad85
I read tcp connections by procfs like this
package main
import (
"fmt"
"github.com/prometheus/procfs"
)
func main() {
fs, _ := procfs.NewDefaultFS()
tcps, _ := fs.NetTCP()
for _, tcp := range tcps {
fmt.Println(tcp.LocalAddr, tcp.LocalPort, tcp.RemAddr, tcp.RemPort, tcp.Inode)
}
}
When I execute multiple times, I find that the same TCP connection appears twice. eg：
Tue Sep 26 18:48 [root@host ~]# ./nettcp | sort | uniq -c | grep '2 '
......
1 192.168.0.2 22815 127.0.0.1 8181 4157386808
2 192.168.0.2 24219 127.0.0.1 8300 4192187746
1 192.168.0.2 29727 127.0.0.1 5002 4185948034
......
But, When I execute multiple netstat command, there won't be the phenomenon mentioned above. eg:
Tue Sep 26 18:50 [root@host ~]# netstat -npta | awk '{print $1, $4, $5, $7}' | sort | uniq -c
......
1 tcp 192.168.0.2:11609 127.0.0.1:8300 138167/python
1 tcp 192.168.0.2:12385 127.0.0.1:8300 138188/python
1 tcp 192.168.0.2:12465 127.0.0.1:8035 266462/agent
......
And I find netstat source code, find the code that
FILE *proc_fopen(const char *name)
{
static char *buffer;
static size_t pagesz;
FILE *fd = fopen(name, "r");
if (fd == NULL)
return NULL;
if (!buffer) {
pagesz = getpagesize();
buffer = malloc(pagesz);
}
setvbuf(fd, buffer, _IOFBF, pagesz);
return fd;
}netstat sets the setvbuf to _IOFBF mode when opening the net/tcp file. But golang procfs doesn't set this.
How can we ensure consistency when reading net/tcp in Golang?