Tizian-Maxime-Weigt/l3-l4-forwarding-in-xdp
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Tizian-Maxime-Weigt
2025-10-27 21:34:08 +00:00
parent e432998063
commit 439f0f9a81
1 changed files with 35 additions and 25 deletions
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main.c
+35 -25
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@@ -8,18 +8,28 @@
#include <linux/ipv6.h>
#include <linux/udp.h>
#include <linux/tcp.h>
#include <linux/types.h>
#include <bpf/bpf_helpers.h>
#include <bpf/bpf_endian.h>
#define IPV6_FLOWINFO_MASK cpu_to_be32(0x0FFFFFFF)
#ifndef AF_INET
#define AF_INET 2
#endif
#ifndef AF_INET6
#define AF_INET6 10
#endif
#define IPV6_FLOWINFO_MASK bpf_htonl(0x0FFFFFFF)
/* Forwarding ports */
struct bpf_map_def SEC("maps") xdp_l3fwd_ports = {
.type = BPF_MAP_TYPE_DEVMAP,
.key_size = sizeof(int),
.value_size = sizeof(int),
.max_entries = 512,
};
struct {
__uint(type, BPF_MAP_TYPE_DEVMAP);
__uint(key_size, sizeof(int));
__uint(value_size, sizeof(int));
__uint(max_entries, 512);
} xdp_l3fwd_ports SEC(".maps");
/* Stats key — identifies a connection or flow */
struct flow_key {
@@ -44,19 +54,19 @@ struct flow_stats {
};
/* Hash map to track stats per flow */
struct bpf_map_def SEC("maps") xdp_flow_stats = {
.type = BPF_MAP_TYPE_HASH,
.key_size = sizeof(struct flow_key),
.value_size = sizeof(struct flow_stats),
.max_entries = 65536,
};
struct {
__uint(type, BPF_MAP_TYPE_HASH);
__uint(key_size, sizeof(struct flow_key));
__uint(value_size, sizeof(struct flow_stats));
__uint(max_entries, 65536);
} xdp_flow_stats SEC(".maps");
/* Decrease IPv4 TTL helper */
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));
__u32 check = (__u32)iph->check;
check += (__u32)bpf_htons(0x0100);
iph->check = (__sum16)(check + (check >= 0xFFFF));
return --iph->ttl;
}
@@ -78,7 +88,7 @@ static __always_inline void record_stats(struct xdp_md *ctx, struct flow_key *ke
}
}
static __always_inline int xdp_l3fwd_flags(struct xdp_md *ctx, u32 flags)
static __always_inline int xdp_l3fwd_flags(struct xdp_md *ctx, __u32 flags)
{
void *data_end = (void *)(long)ctx->data_end;
void *data = (void *)(long)ctx->data;
@@ -86,8 +96,8 @@ static __always_inline int xdp_l3fwd_flags(struct xdp_md *ctx, u32 flags)
struct ethhdr *eth = data;
struct ipv6hdr *ip6h;
struct iphdr *iph;
u16 h_proto;
u64 nh_off;
__u16 h_proto;
__u64 nh_off;
int rc;
nh_off = sizeof(*eth);
@@ -100,7 +110,7 @@ static __always_inline int xdp_l3fwd_flags(struct xdp_md *ctx, u32 flags)
struct flow_key key = {};
__u64 bytes = data_end - data;
if (h_proto == htons(ETH_P_IP)) {
if (h_proto == bpf_htons(ETH_P_IP)) {
iph = data + nh_off;
if ((void *)(iph + 1) > data_end)
return XDP_DROP;
@@ -131,11 +141,11 @@ static __always_inline int xdp_l3fwd_flags(struct xdp_md *ctx, u32 flags)
fib_params.family = AF_INET;
fib_params.tos = iph->tos;
fib_params.l4_protocol = iph->protocol;
fib_params.tot_len = ntohs(iph->tot_len);
fib_params.tot_len = bpf_ntohs(iph->tot_len);
fib_params.ipv4_src = iph->saddr;
fib_params.ipv4_dst = iph->daddr;
} else if (h_proto == htons(ETH_P_IPV6)) {
} else if (h_proto == bpf_htons(ETH_P_IPV6)) {
ip6h = data + nh_off;
if ((void *)(ip6h + 1) > data_end)
return XDP_DROP;
@@ -166,7 +176,7 @@ static __always_inline int xdp_l3fwd_flags(struct xdp_md *ctx, u32 flags)
fib_params.family = AF_INET6;
fib_params.flowinfo = *(__be32 *)ip6h & IPV6_FLOWINFO_MASK;
fib_params.l4_protocol = ip6h->nexthdr;
fib_params.tot_len = ntohs(ip6h->payload_len);
fib_params.tot_len = bpf_ntohs(ip6h->payload_len);
__builtin_memcpy(fib_params.ipv6_src, &ip6h->saddr, 16);
__builtin_memcpy(fib_params.ipv6_dst, &ip6h->daddr, 16);
} else {
@@ -179,9 +189,9 @@ static __always_inline int xdp_l3fwd_flags(struct xdp_md *ctx, u32 flags)
if (!bpf_map_lookup_elem(&xdp_l3fwd_ports, &fib_params.ifindex))
return XDP_PASS;
if (h_proto == htons(ETH_P_IP))
if (h_proto == bpf_htons(ETH_P_IP))
ip_decrease_ttl(iph);
else if (h_proto == htons(ETH_P_IPV6))
else if (h_proto == bpf_htons(ETH_P_IPV6))
ip6h->hop_limit--;
__builtin_memcpy(eth->h_dest, fib_params.dmac, ETH_ALEN);