From ca78801a81e04a31f8088e96b2649a9cbace5499 Mon Sep 17 00:00:00 2001 From: Peter Oskolkov Date: Wed, 13 Feb 2019 11:53:37 -0800 Subject: [PATCH] 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 Signed-off-by: Alexei Starovoitov --- net/core/lwt_bpf.c | 67 ++++++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 65 insertions(+), 2 deletions(-) diff --git a/net/core/lwt_bpf.c b/net/core/lwt_bpf.c index e5a9850d9f48..079871fc020f 100644 --- a/net/core/lwt_bpf.c +++ b/net/core/lwt_bpf.c @@ -16,6 +16,7 @@ #include #include #include +#include struct bpf_lwt_prog { struct bpf_prog *prog; @@ -390,10 +391,72 @@ static const struct lwtunnel_encap_ops bpf_encap_ops = { .owner = THIS_MODULE, }; +static int handle_gso_type(struct sk_buff *skb, unsigned int gso_type, + int encap_len) +{ + struct skb_shared_info *shinfo = skb_shinfo(skb); + + gso_type |= SKB_GSO_DODGY; + shinfo->gso_type |= gso_type; + skb_decrease_gso_size(shinfo, encap_len); + shinfo->gso_segs = 0; + return 0; +} + static int handle_gso_encap(struct sk_buff *skb, bool ipv4, int encap_len) { - /* Handling of GSO-enabled packets is added in the next patch. */ - return -EOPNOTSUPP; + int next_hdr_offset; + void *next_hdr; + __u8 protocol; + + /* SCTP and UDP_L4 gso need more nuanced handling than what + * handle_gso_type() does above: skb_decrease_gso_size() is not enough. + * So at the moment only TCP GSO packets are let through. + */ + if (!(skb_shinfo(skb)->gso_type & (SKB_GSO_TCPV4 | SKB_GSO_TCPV6))) + return -ENOTSUPP; + + if (ipv4) { + protocol = ip_hdr(skb)->protocol; + next_hdr_offset = sizeof(struct iphdr); + next_hdr = skb_network_header(skb) + next_hdr_offset; + } else { + protocol = ipv6_hdr(skb)->nexthdr; + next_hdr_offset = sizeof(struct ipv6hdr); + next_hdr = skb_network_header(skb) + next_hdr_offset; + } + + switch (protocol) { + case IPPROTO_GRE: + next_hdr_offset += sizeof(struct gre_base_hdr); + if (next_hdr_offset > encap_len) + return -EINVAL; + + if (((struct gre_base_hdr *)next_hdr)->flags & GRE_CSUM) + return handle_gso_type(skb, SKB_GSO_GRE_CSUM, + encap_len); + return handle_gso_type(skb, SKB_GSO_GRE, encap_len); + + case IPPROTO_UDP: + next_hdr_offset += sizeof(struct udphdr); + if (next_hdr_offset > encap_len) + return -EINVAL; + + if (((struct udphdr *)next_hdr)->check) + return handle_gso_type(skb, SKB_GSO_UDP_TUNNEL_CSUM, + encap_len); + return handle_gso_type(skb, SKB_GSO_UDP_TUNNEL, encap_len); + + case IPPROTO_IP: + case IPPROTO_IPV6: + if (ipv4) + return handle_gso_type(skb, SKB_GSO_IPXIP4, encap_len); + else + return handle_gso_type(skb, SKB_GSO_IPXIP6, encap_len); + + default: + return -EPROTONOSUPPORT; + } } int bpf_lwt_push_ip_encap(struct sk_buff *skb, void *hdr, u32 len, bool ingress)