260 lines
6.3 KiB
C
260 lines
6.3 KiB
C
#define KBUILD_MODNAME "xdp_l3fwd"
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#include <linux/bpf.h>
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#include <linux/in.h>
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#include <linux/if_ether.h>
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#include <linux/if_packet.h>
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#include <linux/if_vlan.h>
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#include <linux/ip.h>
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#include <linux/ipv6.h>
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#include <linux/udp.h>
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#include <linux/tcp.h>
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#include <linux/types.h>
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#include <bpf/bpf_helpers.h>
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#include <bpf/bpf_endian.h>
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#ifndef AF_INET
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#define AF_INET 2
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#endif
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#ifndef AF_INET6
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#define AF_INET6 10
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#endif
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#define IPV6_FLOWINFO_MASK bpf_htonl(0x0FFFFFFF)
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#define VLAN_MAX_DEPTH 2 /* Support double-tagged VLANs */
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/* Forwarding ports */
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struct {
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__uint(type, BPF_MAP_TYPE_DEVMAP);
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__uint(key_size, sizeof(int));
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__uint(value_size, sizeof(int));
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__uint(max_entries, 512);
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} xdp_l3fwd_ports SEC(".maps");
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/* Stats key — identifies a connection or flow */
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struct flow_key {
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__u8 proto;
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__u8 pad[3]; /* alignment */
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__u16 vlan_id; /* VLAN ID (0 if untagged) */
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__u16 pad2; /* alignment */
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union {
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__u32 ipv4_src;
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__u8 ipv6_src[16];
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};
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union {
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__u32 ipv4_dst;
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__u8 ipv6_dst[16];
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};
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__u16 sport;
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__u16 dport;
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};
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/* Stats value — counts packets and bytes */
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struct flow_stats {
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__u64 packets;
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__u64 bytes;
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};
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/* Hash map to track stats per flow */
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struct {
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__uint(type, BPF_MAP_TYPE_HASH);
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__uint(key_size, sizeof(struct flow_key));
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__uint(value_size, sizeof(struct flow_stats));
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__uint(max_entries, 65536);
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} xdp_flow_stats SEC(".maps");
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/* Decrease IPv4 TTL helper */
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static __always_inline int ip_decrease_ttl(struct iphdr *iph)
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{
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__u32 check = (__u32)iph->check;
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check += (__u32)bpf_htons(0x0100);
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iph->check = (__sum16)(check + (check >= 0xFFFF));
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return --iph->ttl;
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}
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/* Record stats in the xdp_flow_stats map */
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static __always_inline void record_stats(struct xdp_md *ctx, struct flow_key *key, __u64 bytes)
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{
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struct flow_stats *stats;
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stats = bpf_map_lookup_elem(&xdp_flow_stats, key);
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if (stats) {
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__sync_fetch_and_add(&stats->packets, 1);
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__sync_fetch_and_add(&stats->bytes, bytes);
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} else {
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struct flow_stats new_stats = {
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.packets = 1,
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.bytes = bytes,
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};
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bpf_map_update_elem(&xdp_flow_stats, key, &new_stats, BPF_ANY);
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}
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}
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/* Parse VLAN headers and return next protocol and offset */
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static __always_inline int parse_vlan(void *data, void *data_end, __u64 *nh_off, __u16 *h_proto, __u16 *vlan_id)
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{
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struct vlan_hdr {
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__be16 h_vlan_TCI;
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__be16 h_vlan_encapsulated_proto;
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} *vhdr;
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int i;
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/* Parse up to VLAN_MAX_DEPTH VLAN headers */
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#pragma unroll
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for (i = 0; i < VLAN_MAX_DEPTH; i++) {
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if (*h_proto != bpf_htons(ETH_P_8021Q) && *h_proto != bpf_htons(ETH_P_8021AD))
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break;
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vhdr = data + *nh_off;
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if ((void *)(vhdr + 1) > data_end)
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return -1;
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/* Store the outermost VLAN ID */
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if (i == 0)
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*vlan_id = bpf_ntohs(vhdr->h_vlan_TCI) & 0x0FFF;
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*nh_off += sizeof(*vhdr);
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*h_proto = vhdr->h_vlan_encapsulated_proto;
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}
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return 0;
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}
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static __always_inline int xdp_l3fwd_flags(struct xdp_md *ctx, __u32 flags)
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{
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void *data_end = (void *)(long)ctx->data_end;
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void *data = (void *)(long)ctx->data;
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struct bpf_fib_lookup fib_params;
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struct ethhdr *eth = data;
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struct ipv6hdr *ip6h;
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struct iphdr *iph;
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__u16 h_proto;
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__u64 nh_off;
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int rc;
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__u16 vlan_id = 0;
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nh_off = sizeof(*eth);
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if (data + nh_off > data_end)
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return XDP_DROP;
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__builtin_memset(&fib_params, 0, sizeof(fib_params));
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h_proto = eth->h_proto;
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/* Parse VLAN headers if present */
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if (parse_vlan(data, data_end, &nh_off, &h_proto, &vlan_id) < 0)
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return XDP_DROP;
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struct flow_key key = {};
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key.vlan_id = vlan_id;
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__u64 bytes = data_end - data;
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if (h_proto == bpf_htons(ETH_P_IP)) {
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iph = data + nh_off;
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if ((void *)(iph + 1) > data_end)
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return XDP_DROP;
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key.proto = iph->protocol;
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key.ipv4_src = iph->saddr;
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key.ipv4_dst = iph->daddr;
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void *l4_hdr = (void *)iph + (iph->ihl * 4);
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if (l4_hdr + sizeof(struct udphdr) <= data_end) {
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if (iph->protocol == IPPROTO_TCP) {
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struct tcphdr *tcph = l4_hdr;
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key.sport = tcph->source;
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key.dport = tcph->dest;
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} else if (iph->protocol == IPPROTO_UDP) {
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struct udphdr *udph = l4_hdr;
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key.sport = udph->source;
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key.dport = udph->dest;
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}
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}
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/* Record stats before forwarding */
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record_stats(ctx, &key, bytes);
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if (iph->ttl <= 1)
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return XDP_PASS;
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fib_params.family = AF_INET;
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fib_params.tos = iph->tos;
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fib_params.l4_protocol = iph->protocol;
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fib_params.tot_len = bpf_ntohs(iph->tot_len);
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fib_params.ipv4_src = iph->saddr;
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fib_params.ipv4_dst = iph->daddr;
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} else if (h_proto == bpf_htons(ETH_P_IPV6)) {
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ip6h = data + nh_off;
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if ((void *)(ip6h + 1) > data_end)
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return XDP_DROP;
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key.proto = ip6h->nexthdr;
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__builtin_memcpy(key.ipv6_src, &ip6h->saddr, 16);
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__builtin_memcpy(key.ipv6_dst, &ip6h->daddr, 16);
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void *l4_hdr = (void *)(ip6h + 1);
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if (l4_hdr + sizeof(struct udphdr) <= data_end) {
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if (ip6h->nexthdr == IPPROTO_TCP) {
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struct tcphdr *tcph = l4_hdr;
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key.sport = tcph->source;
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key.dport = tcph->dest;
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} else if (ip6h->nexthdr == IPPROTO_UDP) {
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struct udphdr *udph = l4_hdr;
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key.sport = udph->source;
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key.dport = udph->dest;
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}
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}
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/* Record stats before forwarding */
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record_stats(ctx, &key, bytes);
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if (ip6h->hop_limit <= 1)
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return XDP_PASS;
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fib_params.family = AF_INET6;
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fib_params.flowinfo = *(__be32 *)ip6h & IPV6_FLOWINFO_MASK;
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fib_params.l4_protocol = ip6h->nexthdr;
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fib_params.tot_len = bpf_ntohs(ip6h->payload_len);
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__builtin_memcpy(fib_params.ipv6_src, &ip6h->saddr, 16);
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__builtin_memcpy(fib_params.ipv6_dst, &ip6h->daddr, 16);
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} else {
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return XDP_PASS;
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}
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fib_params.ifindex = ctx->ingress_ifindex;
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rc = bpf_fib_lookup(ctx, &fib_params, sizeof(fib_params), flags);
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if (rc == BPF_FIB_LKUP_RET_SUCCESS) {
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if (!bpf_map_lookup_elem(&xdp_l3fwd_ports, &fib_params.ifindex))
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return XDP_PASS;
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if (h_proto == bpf_htons(ETH_P_IP))
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ip_decrease_ttl(iph);
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else if (h_proto == bpf_htons(ETH_P_IPV6))
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ip6h->hop_limit--;
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__builtin_memcpy(eth->h_dest, fib_params.dmac, ETH_ALEN);
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__builtin_memcpy(eth->h_source, fib_params.smac, ETH_ALEN);
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return bpf_redirect_map(&xdp_l3fwd_ports, fib_params.ifindex, 0);
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}
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return XDP_PASS;
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}
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SEC("xdp_l3fwd")
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int xdp_l3fwd_prog(struct xdp_md *ctx)
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{
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return xdp_l3fwd_flags(ctx, 0);
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}
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SEC("xdp_l3fwd_direct")
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int xdp_l3fwd_direct_prog(struct xdp_md *ctx)
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{
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return xdp_l3fwd_flags(ctx, BPF_FIB_LOOKUP_DIRECT);
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}
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char _license[] SEC("license") = "GPL";
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