af_packet / TX_RING not fully non-blocking (w/ MSG_DONTWAIT).

This patch fixes an issue where the send(MSG_DONTWAIT) call
on a TX_RING is not fully non-blocking in cases where the device's sndBuf is
full. We pass nonblock=true to sock_alloc_send_skb() and return any possibly
occuring error code (most likely EGAIN) to the caller. As the fast-path stays
as it is, we keep the unlikely() around skb == NULL.

Signed-off-by: Mathias Kretschmer <mathias.kretschmer@fokus.fraunhofer.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index 5102c3cc4eec4ecec6698859935d7769d37a174c..b5989c6ee5513904127a8ffec31d09589094c8f6 100644 (file)
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -2311,11 +2311,14 @@ static int tpacket_snd(struct packet_sock *po, struct msghdr *msg)
                tlen = dev->needed_tailroom;
                skb = sock_alloc_send_skb(&po->sk,
                                hlen + tlen + sizeof(struct sockaddr_ll),
-                               0, &err);
+                               !need_wait, &err);
 
-               if (unlikely(skb == NULL))
+               if (unlikely(skb == NULL)) {
+                       /* we assume the socket was initially writeable ... */
+                       if (likely(len_sum > 0))
+                               err = len_sum;
                        goto out_status;
-
+               }
                tp_len = tpacket_fill_skb(po, skb, ph, dev, size_max, proto,
                                          addr, hlen);
                if (tp_len > dev->mtu + dev->hard_header_len) {