diff options
| author | David Ahern <dsahern@gmail.com> | 2018-05-15 16:20:52 -0700 |
|---|---|---|
| committer | Daniel Borkmann <daniel@iogearbox.net> | 2018-05-16 22:04:52 +0200 |
| commit | 44edef77bd92730e1520b07f5ae2c9f4628738a8 (patch) | |
| tree | c974f9f6e52e873b0444c3f8f634741fbf74c88f /samples/bpf/xdp_fwd_kern.c | |
| parent | 5b26ace65012cbf3b54a68c39041bcd8ae5e31a7 (diff) | |
| download | lwn-44edef77bd92730e1520b07f5ae2c9f4628738a8.tar.gz lwn-44edef77bd92730e1520b07f5ae2c9f4628738a8.zip | |
samples/bpf: Decrement ttl in fib forwarding example
Only consider forwarding packets if ttl in received packet is > 1 and
decrement ttl before handing off to bpf_redirect_map.
Signed-off-by: David Ahern <dsahern@gmail.com>
Acked-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Diffstat (limited to 'samples/bpf/xdp_fwd_kern.c')
| -rw-r--r-- | samples/bpf/xdp_fwd_kern.c | 39 |
1 files changed, 31 insertions, 8 deletions
diff --git a/samples/bpf/xdp_fwd_kern.c b/samples/bpf/xdp_fwd_kern.c index cdf4fc383cc9..4a6be0f87505 100644 --- a/samples/bpf/xdp_fwd_kern.c +++ b/samples/bpf/xdp_fwd_kern.c @@ -30,12 +30,24 @@ struct bpf_map_def SEC("maps") tx_port = { .max_entries = 64, }; +/* from include/net/ip.h */ +static __always_inline int ip_decrease_ttl(struct iphdr *iph) +{ + u32 check = (__force u32)iph->check; + + check += (__force u32)htons(0x0100); + iph->check = (__force __sum16)(check + (check >= 0xFFFF)); + return --iph->ttl; +} + static __always_inline int xdp_fwd_flags(struct xdp_md *ctx, u32 flags) { void *data_end = (void *)(long)ctx->data_end; void *data = (void *)(long)ctx->data; struct bpf_fib_lookup fib_params; struct ethhdr *eth = data; + struct ipv6hdr *ip6h; + struct iphdr *iph; int out_index; u16 h_proto; u64 nh_off; @@ -48,11 +60,14 @@ static __always_inline int xdp_fwd_flags(struct xdp_md *ctx, u32 flags) h_proto = eth->h_proto; if (h_proto == htons(ETH_P_IP)) { - struct iphdr *iph = data + nh_off; + iph = data + nh_off; if (iph + 1 > data_end) return XDP_DROP; + if (iph->ttl <= 1) + return XDP_PASS; + fib_params.family = AF_INET; fib_params.tos = iph->tos; fib_params.l4_protocol = iph->protocol; @@ -64,19 +79,22 @@ static __always_inline int xdp_fwd_flags(struct xdp_md *ctx, u32 flags) } else if (h_proto == htons(ETH_P_IPV6)) { struct in6_addr *src = (struct in6_addr *) fib_params.ipv6_src; struct in6_addr *dst = (struct in6_addr *) fib_params.ipv6_dst; - struct ipv6hdr *iph = data + nh_off; - if (iph + 1 > data_end) + ip6h = data + nh_off; + if (ip6h + 1 > data_end) return XDP_DROP; + if (ip6h->hop_limit <= 1) + return XDP_PASS; + fib_params.family = AF_INET6; - fib_params.flowlabel = *(__be32 *)iph & IPV6_FLOWINFO_MASK; - fib_params.l4_protocol = iph->nexthdr; + fib_params.flowlabel = *(__be32 *)ip6h & IPV6_FLOWINFO_MASK; + fib_params.l4_protocol = ip6h->nexthdr; fib_params.sport = 0; fib_params.dport = 0; - fib_params.tot_len = ntohs(iph->payload_len); - *src = iph->saddr; - *dst = iph->daddr; + fib_params.tot_len = ntohs(ip6h->payload_len); + *src = ip6h->saddr; + *dst = ip6h->daddr; } else { return XDP_PASS; } @@ -92,6 +110,11 @@ static __always_inline int xdp_fwd_flags(struct xdp_md *ctx, u32 flags) * forwarding packets are dropped. */ if (out_index > 0) { + if (h_proto == htons(ETH_P_IP)) + ip_decrease_ttl(iph); + else if (h_proto == htons(ETH_P_IPV6)) + ip6h->hop_limit--; + memcpy(eth->h_dest, fib_params.dmac, ETH_ALEN); memcpy(eth->h_source, fib_params.smac, ETH_ALEN); return bpf_redirect_map(&tx_port, out_index, 0); |