On Wed, 26 Aug 2009, Eric Dumazet wrote:

I think it's already done in udp_sendmsg()>
Code starting at line 765 in net/ipv4/udp.c

        /*
         * ENOBUFS = no kernel mem, SOCK_NOSPACE = no sndbuf space.  Reporting
         * ENOBUFS might not be good (it's not tunable per se), but otherwise
         * we don't have a good statistic (IpOutDiscards but it can be too many
         * things).  We could add another new stat but at least for now that
         * seems like overkill.
         */
        if (err == -ENOBUFS || test_bit(SOCK_NOSPACE, &sk->sk_socket->flags)) {
                UDP_INC_STATS_USER(sock_net(sk),
                                UDP_MIB_SNDBUFERRORS, is_udplite);
        }

Right. That would mean the fix to ip_push_pending_frames() would also fix
UDP tx drop accounting.

ENOBUFS is then returned for two cases.

1. SNDBUF overflow
2. NIC TX overflow

Hope that is not confusing.