Messages in this thread | | | From | Willem de Bruijn <> | Date | Sun, 13 Feb 2022 20:28:45 -0500 | Subject | Re: [PATCH] gso: do not skip outer ip header in case of ipip and net_failover |
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On Sun, Feb 13, 2022 at 10:10 AM Tao Liu <thomas.liu@ucloud.cn> wrote: > > We encouter a tcp drop issue in our cloud environment. Packet GROed in host > forwards to a VM virtio_net nic with net_failover enabled. VM acts as a > IPVS LB with ipip encapsulation. The full path like: > host gro -> vm virtio_net rx -> net_failover rx -> ipvs fullnat > -> ipip encap -> net_failover tx -> virtio_net tx > > When net_failover transmits a ipip pkt (gso_type = 0x0103), there is no gso > performed because it supports TSO and GSO_IPXIP4. But network_header has > been pointing to inner ip header.
If the packet is configured correctly, and net_failover advertises that it can handle TSO packets with IPIP encap, then still virtio_net should not advertise it and software GSO be applied on its dev_queue_xmit call.
This is assuming that the packet not only has SKB_GSO_IPXIP4 correctly set, but also tunneling fields like skb->encapsulated and skb_inner_network_header.
> --- > net/ipv4/af_inet.c | 10 +++++++++- > 1 file changed, 9 insertions(+), 1 deletion(-) > > diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c > index 9c465ba..f8b3f8a 100644 > --- a/net/ipv4/af_inet.c > +++ b/net/ipv4/af_inet.c > @@ -1425,10 +1425,18 @@ struct sk_buff *inet_gso_segment(struct sk_buff *skb, > static struct sk_buff *ipip_gso_segment(struct sk_buff *skb, > netdev_features_t features) > { > + struct sk_buff *segs; > + int nhoff; > + > if (!(skb_shinfo(skb)->gso_type & SKB_GSO_IPXIP4)) > return ERR_PTR(-EINVAL); > > - return inet_gso_segment(skb, features); > + nhoff = skb_network_header(skb) - skb_mac_header(skb); > + segs = inet_gso_segment(skb, features); > + if (!segs) > + skb->network_header = skb_mac_header(skb) + nhoff - skb->head; > + > + return segs; > }
If this would be needed for IPIP, then the same would be needed for SIT, etc.
Is the skb_network_header
1. correctly pointing to the outer header of the TSO packet before the call to inet_gso_segment 2. incorrectly pointing to the inner header of the (still) TSO packet after the call to inet_gso_segment
inet_gso_segment already does the same operation: save nhoff, pull network header, call callbacks.gso_segment (which can be ipip_gso_segment->inet_gso_segment), then place the network header back at nhoff.
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