Re: How to get creatior PID information for the local tcp connection

From: Eric Dumazet
Date: Thu Apr 07 2016 - 14:26:49 EST


On Thu, 2016-04-07 at 23:01 +0530, Vishnu Pratap Singh wrote:
> Hi,
>
>
> Issue - How to get PID information for the local tcp connection
>
>
>
> i want to get the creator PID for each socket in user space for local
> tcp connection, i see in kernel there is support for returing PID with
> "SO_PEERCRED" ioctl to work across namespaces. it uses struct pid and
> struct cred to store the peer credentials on struct sock.
> cred_to_ucred(sk->sk_peer_pid, sk->sk_peer_cred, &peercred); Above
> function stores the PID information in ucred->pid = pid_vnr(pid); and
> same is returned via "SO_PEERCRED" ioctl .
>
> But for local tcp connection i get pid as 0, is there any way i can
> get the PID information. Any help or suggestion will be highly
> helpful.
>
>

man 7 socket

SO_PEERCRED
Return the credentials of the foreign process connected to this socket.
This is possible only for connected AF_UNIX stream sockets and AF_UNIX
stream and datagram socket pairs created using socketpair(2); see unix(7).
The returned credentials are those that were in effect at the time of the
call to connect(2) or socketpair(2). The argument is a ucred structure;
define the GNU_SOURCE feature test macro to obtain the definition of that
structure from <sys/socket.h>. This socket option is read-only.