Willem de Bruijn
2022-Apr-20 13:45 UTC
[PATCH net-next] net/af_packet: add VLAN support for AF_PACKET SOCK_RAW GSO
On Wed, Apr 20, 2022 at 4:28 AM Hangbin Liu <liuhangbin at gmail.com> wrote:> > Currently, the kernel drops GSO VLAN tagged packet if it's created with > socket(AF_PACKET, SOCK_RAW, 0) plus virtio_net_hdr. > > The reason is AF_PACKET doesn't adjust the skb network header if there is > a VLAN tag. Then after virtio_net_hdr_set_proto() called, the skb->protocol > will be set to ETH_P_IP/IPv6. And in later inet/ipv6_gso_segment() the skb > is dropped as network header position is invalid. > > Let's handle VLAN packets by adjusting network header position in > packet_parse_headers(), and move the function in packet_snd() before > calling virtio_net_hdr_set_proto().The network header is set in skb_reset_network_header(skb); err = -EINVAL; if (sock->type == SOCK_DGRAM) { offset = dev_hard_header(skb, dev, ntohs(proto), addr, NULL, len); if (unlikely(offset < 0)) goto out_free; } else if (reserve) { skb_reserve(skb, -reserve); if (len < reserve + sizeof(struct ipv6hdr) && dev->min_header_len != dev->hard_header_len) skb_reset_network_header(skb); } If all that is needed is to move the network header beyond an optional VLAN tag in the case of SOCK_RAW, then this can be done in the else for Ethernet packets. It is not safe to increase reserve, as that would eat into the reserved hlen LL_RESERVED_SPACE(dev), which does not account for optional VLAN headers. Instead of setting here first, then patching up again later in packet_parse_headers. This change affects all packets with VLAN headers, not just those with GSO. I imagine that moving the network header is safe for all, but don't know that code well enough to verify that it does not have unintended side effects. Does dev_queue_xmit expect the network header to point to the start of the VLAN headers or after, for instance?> No need to update tpacket_snd() as it calls packet_parse_headers() in > tpacket_fill_skb(), which is already before calling virtio_net_hdr_* > functions. > > skb->no_fcs setting is also moved upper to make all skb settings together > and keep consistence with function packet_sendmsg_spkt(). > > Signed-off-by: Hangbin Liu <liuhangbin at gmail.com> > --- > net/packet/af_packet.c | 18 +++++++++++++----- > 1 file changed, 13 insertions(+), 5 deletions(-) > > diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c > index 002d2b9c69dd..cfdbda28ef82 100644 > --- a/net/packet/af_packet.c > +++ b/net/packet/af_packet.c > @@ -1924,12 +1924,20 @@ static int packet_rcv_spkt(struct sk_buff *skb, struct net_device *dev, > > static void packet_parse_headers(struct sk_buff *skb, struct socket *sock) > { > + int depth; > + > if ((!skb->protocol || skb->protocol == htons(ETH_P_ALL)) && > sock->type == SOCK_RAW) { > skb_reset_mac_header(skb); > skb->protocol = dev_parse_header_protocol(skb); > } > > + /* Move network header to the right position for VLAN tagged packets */ > + if (likely(skb->dev->type == ARPHRD_ETHER) && > + eth_type_vlan(skb->protocol) && > + __vlan_get_protocol(skb, skb->protocol, &depth) != 0) > + skb_set_network_header(skb, depth); > + > skb_probe_transport_header(skb); > } > > @@ -3047,6 +3055,11 @@ static int packet_snd(struct socket *sock, struct msghdr *msg, size_t len) > skb->mark = sockc.mark; > skb->tstamp = sockc.transmit_time; > > + if (unlikely(extra_len == 4)) > + skb->no_fcs = 1; > + > + packet_parse_headers(skb, sock); > + > if (has_vnet_hdr) { > err = virtio_net_hdr_to_skb(skb, &vnet_hdr, vio_le()); > if (err) > @@ -3055,11 +3068,6 @@ static int packet_snd(struct socket *sock, struct msghdr *msg, size_t len) > virtio_net_hdr_set_proto(skb, &vnet_hdr); > } > > - packet_parse_headers(skb, sock); > - > - if (unlikely(extra_len == 4)) > - skb->no_fcs = 1; > - > err = po->xmit(skb); > if (unlikely(err != 0)) { > if (err > 0) > -- > 2.35.1 >