Re: [PATCH] net/packet: fix packet drop as of virtio gso

[Jason Wang]

On 2018年09月29日 23:41, Jianfeng Tan wrote:
When we use raw socket as the vhost backend, a packet from virito with
gso offloading information, cannot be sent out in later validaton at
xmit path, as we did not set correct skb->protocol which is further used
for looking up the gso function.

Hi:

May I ask the reason for using raw socket for vhost? It was not a common 
setup with little care in the past few years. And it was slow since it 
lacks some recent improvements. Can it be replaced with e.g macvtap?

Thanks


To fix this, we set this field according to virito hdr information.

Fixes: e858fae2b0b8f4 ("virtio_net: use common code for virtio_net_hdr and skb GSO 
conversion")

Cc: sta...@vger.kernel.org
Signed-off-by: Jianfeng Tan <jianfeng....@linux.alibaba.com>
---
  include/linux/virtio_net.h | 18 ++++++++++++++++++
  net/packet/af_packet.c     | 11 +++++++----
  2 files changed, 25 insertions(+), 4 deletions(-)

diff --git a/include/linux/virtio_net.h b/include/linux/virtio_net.h
index 9397628a1967..cb462f9ab7dd 100644
--- a/include/linux/virtio_net.h
+++ b/include/linux/virtio_net.h
@@ -5,6 +5,24 @@
  #include <linux/if_vlan.h>
  #include <uapi/linux/virtio_net.h>
  
+static inline int virtio_net_hdr_set_proto(struct sk_buff *skb,
+                                          const struct virtio_net_hdr *hdr)
+{
+       switch (hdr->gso_type & ~VIRTIO_NET_HDR_GSO_ECN) {
+       case VIRTIO_NET_HDR_GSO_TCPV4:
+       case VIRTIO_NET_HDR_GSO_UDP:
+               skb->protocol = cpu_to_be16(ETH_P_IP);
+               break;
+       case VIRTIO_NET_HDR_GSO_TCPV6:
+               skb->protocol = cpu_to_be16(ETH_P_IPV6);
+               break;
+       default:
+               return -EINVAL;
+       }
+
+       return 0;
+}
+
  static inline int virtio_net_hdr_to_skb(struct sk_buff *skb,
                                        const struct virtio_net_hdr *hdr,
                                        bool little_endian)
diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index 75c92a87e7b2..d6e94dc7e290 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -2715,10 +2715,12 @@ static int tpacket_snd(struct packet_sock *po, struct 
msghdr *msg)
                        }
                }
  
-		if (po->has_vnet_hdr && virtio_net_hdr_to_skb(skb, vnet_hdr,
-                                                             vio_le())) {
-                       tp_len = -EINVAL;
-                       goto tpacket_error;
+               if (po->has_vnet_hdr) {
+                       if (virtio_net_hdr_to_skb(skb, vnet_hdr, vio_le())) {
+                               tp_len = -EINVAL;
+                               goto tpacket_error;
+                       }
+                       virtio_net_hdr_set_proto(skb, vnet_hdr);
                }
  
  		skb->destructor = tpacket_destruct_skb;
@@ -2915,6 +2917,7 @@ static int packet_snd(struct socket *sock, struct msghdr 
*msg, size_t len)
                if (err)
                        goto out_free;
                len += sizeof(vnet_hdr);
+               virtio_net_hdr_set_proto(skb, &vnet_hdr);
        }
  
  	skb_probe_transport_header(skb, reserve);