bpf: handle GSO in bpf_lwt_push_encap
This patch adds handling of GSO packets in bpf_lwt_push_ip_encap() (called from bpf_lwt_push_encap): * IPIP, GRE, and UDP encapsulation types are deduced by looking into iphdr->protocol or ipv6hdr->next_header; * SCTP GSO packets are not supported (as bpf_skb_proto_4_to_6 and similar do); * UDP_L4 GSO packets are also not supported (although they are not blocked in bpf_skb_proto_4_to_6 and similar), as skb_decrease_gso_size() will break it; * SKB_GSO_DODGY bit is set. Note: it may be possible to support SCTP and UDP_L4 gso packets; but as these cases seem to be not well handled by other tunneling/encapping code paths, the solution should be generic enough to apply to all tunneling/encapping code. v8 changes: - make sure that if GRE or UDP encap is detected, there is enough of pushed bytes to cover both IP[v6] + GRE|UDP headers; - do not reject double-encapped packets; - whitelist TCP GSO packets rather than block SCTP GSO and UDP GSO. Signed-off-by:Peter Oskolkov <posk@google.com> Signed-off-by:
Alexei Starovoitov <ast@kernel.org>
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