sctp: Add buffer utilization fields to /proc/net/sctp/assocs

sctp: Add buffer utilization fields to /proc/net/sctp/assocs

This patch adds the following fields to /proc/net/sctp/assocs output:

	- sk->sk_wmem_alloc as "wmema"	(transmit queue bytes committed)
	- sk->sk_wmem_queued as "wmemq"	(persistent queue size)
	- sk->sk_sndbuf as "sndbuf"	(size of send buffer in bytes)
	- sk->sk_rcvbuf as "rcvbuf"	(size of receive buffer in bytes)

When small DATA chunks containing 136 bytes data are sent the TX_QUEUE
(assoc->sndbuf_used) reaches a maximum of 40.9% of sk_sndbuf value when
peer.rwnd = 0. This was diagnosed from sk_wmem_alloc value reaching maximum
value of sk_sndbuf.

TX_QUEUE (assoc->sndbuf_used), sk_wmem_alloc and sk_wmem_queued values are
incremented in sctp_set_owner_w() for outgoing data chunks. Having access to
the above values in /proc/net/sctp/assocs will provide a better understanding
of SCTP buffer management.

With patch applied, example output when peer.rwnd = 0

where:
    ASSOC ffff880132298000 is sender
          ffff880125343000 is receiver

 ASSOC           SOCK            STY SST ST  HBKT ASSOC-ID TX_QUEUE RX_QUEUE \
ffff880132298000 ffff880124a0a0c0 2   1   3  29325    1      214656        0 \
ffff880125343000 ffff8801237d7700 2   1   3  36210    2           0   524520 \

UID   INODE LPORT  RPORT LADDRS <-> RADDRS       HBINT   INS  OUTS \
  0   25108 3455   3456  *10.4.8.3 <-> *10.5.8.3  7500     2     2 \
  0   27819 3456   3455  *10.5.8.3 <-> *10.4.8.3  7500     2     2 \

MAXRT T1X T2X RTXC   wmema   wmemq  sndbuf  rcvbuf
    4   0   0   72  525633  440320  524288  524288
    4   0   0    0       1       0  524288  524288

Signed-off-by: Dilip Daya <dilip.daya@hp.com>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/sctp/proc.c

@@ -295,7 +295,8 @@ static void * sctp_assocs_seq_start(struct seq_file *seq, loff_t *pos)
 		seq_printf(seq, " ASSOC     SOCK   STY SST ST HBKT "
 				"ASSOC-ID TX_QUEUE RX_QUEUE UID INODE LPORT "
 				"RPORT LADDRS <-> RADDRS "
-				"HBINT INS OUTS MAXRT T1X T2X RTXC\n");
+				"HBINT INS OUTS MAXRT T1X T2X RTXC "
+				"wmema wmemq sndbuf rcvbuf\n");
 
 	return (void *)pos;
 }
@@ -349,11 +350,16 @@ static int sctp_assocs_seq_show(struct seq_file *seq, void *v)
 		sctp_seq_dump_local_addrs(seq, epb);
 		seq_printf(seq, "<-> ");
 		sctp_seq_dump_remote_addrs(seq, assoc);
-		seq_printf(seq, "\t%8lu %5d %5d %4d %4d %4d %8d ",
+		seq_printf(seq, "\t%8lu %5d %5d %4d %4d %4d %8d "
+			   "%8d %8d %8d %8d",
 			assoc->hbinterval, assoc->c.sinit_max_instreams,
 			assoc->c.sinit_num_ostreams, assoc->max_retrans,
 			assoc->init_retries, assoc->shutdown_retries,
-			assoc->rtx_data_chunks);
+			assoc->rtx_data_chunks,
+			atomic_read(&sk->sk_wmem_alloc),
+			sk->sk_wmem_queued,
+			sk->sk_sndbuf,
+			sk->sk_rcvbuf);
 		seq_printf(seq, "\n");
 	}
 	read_unlock(&head->lock);