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

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Date:	Thu, 07 Apr 2016 11:31:25 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Vishnu Pratap Singh <vishu13285@...il.com>
Cc:	dccp@...r.kernel.org, linux-kernel@...r.kernel.org,
	netdev@...r.kernel.org,
	"vishnu.ps@...sung.com" <vishnu.ps@...sung.com>
Subject: Re: How to get creatior PID information for the local tcp connection

On Thu, 2016-04-07 at 11:26 -0700, Eric Dumazet wrote:
> 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.
> 

Sorry, I hit "Send" too fast.

This is not implemented for TCP yet.

You'll have to take a look at iproute2 package, since "ss -tp" is able
to find this information, by looking at all /proc/{pid}/fd/*  files and
the socket inode number the kernel gives through inet_diag

Not scalable if you have millions of sockets...