Commit 6ce9e7b5 authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

ip: Report qdisc packet drops 



Christoph Lameter pointed out that packet drops at qdisc level where not
accounted in SNMP counters. Only if application sets IP_RECVERR, drops
are reported to user (-ENOBUFS errors) and SNMP counters updated.

IP_RECVERR is used to enable extended reliable error message passing,
but these are not needed to update system wide SNMP stats.

This patch changes things a bit to allow SNMP counters to be updated,
regardless of IP_RECVERR being set or not on the socket.

Example after an UDP tx flood
# netstat -s 
...
IP:
    1487048 outgoing packets dropped
...
Udp:
...
    SndbufErrors: 1487048


send() syscalls, do however still return an OK status, to not
break applications.

Note : send() manual page explicitly says for -ENOBUFS error :

 "The output queue for a network interface was full.
  This generally indicates that the interface has stopped sending,
  but may be caused by transient congestion.
  (Normally, this does not occur in Linux. Packets are just silently
  dropped when a device queue overflows.) "

This is not true for IP_RECVERR enabled sockets : a send() syscall
that hit a qdisc drop returns an ENOBUFS error.

Many thanks to Christoph, David, and last but not least, Alexey !

Signed-off-by: default avatarEric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 2e59af3d

net/ipv4/ip_output.c

+1 −1
Original line number Diff line number Diff line
@@ -1302,7 +1302,7 @@ int ip_push_pending_frames(struct sock *sk) 
	err = ip_local_out(skb);

	if (err) {

		if (err > 0)

			err = inet->recverr ? net_xmit_errno(err) : 0;

			err = net_xmit_errno(err);

		if (err)

			goto error;

	}

net/ipv4/raw.c

+7 −2
Original line number Diff line number Diff line
@@ -375,7 +375,7 @@ static int raw_send_hdrinc(struct sock *sk, void *from, size_t length, 
	err = NF_HOOK(PF_INET, NF_INET_LOCAL_OUT, skb, NULL, rt->u.dst.dev,

		      dst_output);

	if (err > 0)

		err = inet->recverr ? net_xmit_errno(err) : 0;

		err = net_xmit_errno(err);

	if (err)

		goto error;

out:
@@ -386,6 +386,8 @@ error_fault: 
	kfree_skb(skb);

error:

	IP_INC_STATS(net, IPSTATS_MIB_OUTDISCARDS);

	if (err == -ENOBUFS && !inet->recverr)

		err = 0;

	return err;

}
@@ -576,8 +578,11 @@ back_from_confirm: 
					&ipc, &rt, msg->msg_flags);

		if (err)

			ip_flush_pending_frames(sk);

		else if (!(msg->msg_flags & MSG_MORE))

		else if (!(msg->msg_flags & MSG_MORE)) {

			err = ip_push_pending_frames(sk);

			if (err == -ENOBUFS && !inet->recverr)

				err = 0;

		}

		release_sock(sk);

	}

done:

net/ipv4/udp.c

+9 −3
Original line number Diff line number Diff line
@@ -561,12 +561,18 @@ static int udp_push_pending_frames(struct sock *sk) 


send:

	err = ip_push_pending_frames(sk);

	if (err) {

		if (err == -ENOBUFS && !inet->recverr) {

			UDP_INC_STATS_USER(sock_net(sk),

					   UDP_MIB_SNDBUFERRORS, is_udplite);

			err = 0;

		}

	} else

		UDP_INC_STATS_USER(sock_net(sk),

				   UDP_MIB_OUTDATAGRAMS, is_udplite);

out:

	up->len = 0;

	up->pending = 0;

	if (!err)

		UDP_INC_STATS_USER(sock_net(sk),

				UDP_MIB_OUTDATAGRAMS, is_udplite);

	return err;

}

net/ipv6/ip6_output.c

+1 −1
Original line number Diff line number Diff line
@@ -1511,7 +1511,7 @@ int ip6_push_pending_frames(struct sock *sk) 
	err = ip6_local_out(skb);

	if (err) {

		if (err > 0)

			err = np->recverr ? net_xmit_errno(err) : 0;

			err = net_xmit_errno(err);

		if (err)

			goto error;

	}

net/ipv6/raw.c

+3 −1
Original line number Diff line number Diff line
@@ -642,7 +642,7 @@ static int rawv6_send_hdrinc(struct sock *sk, void *from, int length, 
	err = NF_HOOK(PF_INET6, NF_INET_LOCAL_OUT, skb, NULL, rt->u.dst.dev,

		      dst_output);

	if (err > 0)

		err = np->recverr ? net_xmit_errno(err) : 0;

		err = net_xmit_errno(err);

	if (err)

		goto error;

out:
@@ -653,6 +653,8 @@ error_fault: 
	kfree_skb(skb);

error:

	IP6_INC_STATS(sock_net(sk), rt->rt6i_idev, IPSTATS_MIB_OUTDISCARDS);

	if (err == -ENOBUFS && !np->recverr)

		err = 0;

	return err;

}

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