Tizian-Maxime-Weigt/l3-l4-forwarding-in-xdp
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Tizian Maxime Weigt 2025-10-28 09:18:45 +00:00
parent a371f54f3a
commit aacb5dd1a4
1 changed files with 17 additions and 18 deletions
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main.c
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@ -59,9 +59,9 @@ struct flow_stats {
__u64 bytes; __u64 bytes;
}; };
/* Hash map to track stats per flow */ /* PERCPU hash map to track stats per flow - NO LOCKING NEEDED */
struct { struct {
__uint(type, BPF_MAP_TYPE_HASH); __uint(type, BPF_MAP_TYPE_PERCPU_HASH);
__uint(key_size, sizeof(struct flow_key)); __uint(key_size, sizeof(struct flow_key));
__uint(value_size, sizeof(struct flow_stats)); __uint(value_size, sizeof(struct flow_stats));
__uint(max_entries, 65536); __uint(max_entries, 65536);
@ -76,21 +76,22 @@ static __always_inline int ip_decrease_ttl(struct iphdr *iph)
return --iph->ttl; return --iph->ttl;
} }
/* Record stats in the xdp_flow_stats map */ /* Record stats in the xdp_flow_stats map - OPTIMIZED for PERCPU */
static __always_inline void record_stats(struct xdp_md *ctx, struct flow_key *key, __u64 bytes) static __always_inline void record_stats(struct xdp_md *ctx, struct flow_key *key, __u64 bytes)
{ {
struct flow_stats *stats; struct flow_stats *stats;
stats = bpf_map_lookup_elem(&xdp_flow_stats, key); stats = bpf_map_lookup_elem(&xdp_flow_stats, key);
if (stats) { if (stats) {
__sync_fetch_and_add(&stats->packets, 1); /* Direct update - no atomics needed with PERCPU maps */
__sync_fetch_and_add(&stats->bytes, bytes); stats->packets++;
stats->bytes += bytes;
} else { } else {
struct flow_stats new_stats = { struct flow_stats new_stats = {
.packets = 1, .packets = 1,
.bytes = bytes, .bytes = bytes,
}; };
bpf_map_update_elem(&xdp_flow_stats, key, &new_stats, BPF_ANY); bpf_map_update_elem(&xdp_flow_stats, key, &new_stats, BPF_NOEXIST);
} }
} }
@ -157,6 +158,9 @@ static __always_inline int xdp_l3fwd_flags(struct xdp_md *ctx, __u32 flags)
if ((void *)(iph + 1) > data_end) if ((void *)(iph + 1) > data_end)
return XDP_DROP; return XDP_DROP;
if (iph->ttl <= 1)
return XDP_PASS;
key.proto = iph->protocol; key.proto = iph->protocol;
key.ipv4_src = iph->saddr; key.ipv4_src = iph->saddr;
key.ipv4_dst = iph->daddr; key.ipv4_dst = iph->daddr;
@ -174,12 +178,6 @@ static __always_inline int xdp_l3fwd_flags(struct xdp_md *ctx, __u32 flags)
} }
} }
/* Record stats before forwarding */
record_stats(ctx, &key, bytes);
if (iph->ttl <= 1)
return XDP_PASS;
fib_params.family = AF_INET; fib_params.family = AF_INET;
fib_params.tos = iph->tos; fib_params.tos = iph->tos;
fib_params.l4_protocol = iph->protocol; fib_params.l4_protocol = iph->protocol;
@ -192,6 +190,9 @@ static __always_inline int xdp_l3fwd_flags(struct xdp_md *ctx, __u32 flags)
if ((void *)(ip6h + 1) > data_end) if ((void *)(ip6h + 1) > data_end)
return XDP_DROP; return XDP_DROP;
if (ip6h->hop_limit <= 1)
return XDP_PASS;
key.proto = ip6h->nexthdr; key.proto = ip6h->nexthdr;
__builtin_memcpy(key.ipv6_src, &ip6h->saddr, 16); __builtin_memcpy(key.ipv6_src, &ip6h->saddr, 16);
__builtin_memcpy(key.ipv6_dst, &ip6h->daddr, 16); __builtin_memcpy(key.ipv6_dst, &ip6h->daddr, 16);
@ -209,12 +210,6 @@ static __always_inline int xdp_l3fwd_flags(struct xdp_md *ctx, __u32 flags)
} }
} }
/* Record stats before forwarding */
record_stats(ctx, &key, bytes);
if (ip6h->hop_limit <= 1)
return XDP_PASS;
fib_params.family = AF_INET6; fib_params.family = AF_INET6;
fib_params.flowinfo = *(__be32 *)ip6h & IPV6_FLOWINFO_MASK; fib_params.flowinfo = *(__be32 *)ip6h & IPV6_FLOWINFO_MASK;
fib_params.l4_protocol = ip6h->nexthdr; fib_params.l4_protocol = ip6h->nexthdr;
@ -227,10 +222,14 @@ static __always_inline int xdp_l3fwd_flags(struct xdp_md *ctx, __u32 flags)
fib_params.ifindex = ctx->ingress_ifindex; fib_params.ifindex = ctx->ingress_ifindex;
rc = bpf_fib_lookup(ctx, &fib_params, sizeof(fib_params), flags); rc = bpf_fib_lookup(ctx, &fib_params, sizeof(fib_params), flags);
if (rc == BPF_FIB_LKUP_RET_SUCCESS) { if (rc == BPF_FIB_LKUP_RET_SUCCESS) {
if (!bpf_map_lookup_elem(&xdp_l3fwd_ports, &fib_params.ifindex)) if (!bpf_map_lookup_elem(&xdp_l3fwd_ports, &fib_params.ifindex))
return XDP_PASS; return XDP_PASS;
/* Record stats AFTER fib lookup */
record_stats(ctx, &key, bytes);
if (h_proto == bpf_htons(ETH_P_IP)) if (h_proto == bpf_htons(ETH_P_IP))
ip_decrease_ttl(iph); ip_decrease_ttl(iph);
else if (h_proto == bpf_htons(ETH_P_IPV6)) else if (h_proto == bpf_htons(ETH_P_IPV6))