sockmap_redirect.c

#include <linux/bpf.h>
#include <sys/socket.h>
#include <bpf/bpf_endian.h>
#include <bpf/bpf_helpers.h>

/* Map local port in host byte order to target socket */
struct {
	__uint(type, BPF_MAP_TYPE_SOCKHASH);
	__uint(max_entries, 1024);
	__type(key, __u32);
	__type(value, __u64);
} sock_map SEC(".maps");

char _license[] SEC("license") = "GPL";

SEC("sk_msg")
int sk_msg_prog(struct sk_msg_md *msg)
{
	__u32 lport = msg->local_port;
	__u32 rport = msg->remote_port;
	
	bpf_printk("SK_MSG: redirecting from local_port=%u remote_port=%u", lport, rport);
	
	// Try to redirect based on local port
	int ret = bpf_msg_redirect_hash(msg, &sock_map, &lport, BPF_F_INGRESS);
	if (ret != SK_PASS) {
		bpf_printk("SK_MSG: redirect failed, ret=%d", ret);
	}
	
	return ret;
}

SEC("sockops")
int sockops_prog(struct bpf_sock_ops *ctx)
{
	__u32 lport = ctx->local_port;
	__u32 rport = bpf_ntohl(ctx->remote_port);
	__u64 cookie = bpf_get_socket_cookie(ctx);

	switch (ctx->op) {
	case BPF_SOCK_OPS_ACTIVE_ESTABLISHED_CB:
		bpf_printk("SOCKOPS: ACTIVE_ESTABLISHED lport=%u rport=%u cookie=%lx", 
			   lport, rport, cookie);
		bpf_sock_hash_update(ctx, &sock_map, &lport, BPF_ANY);
		break;
	case BPF_SOCK_OPS_PASSIVE_ESTABLISHED_CB:
		bpf_printk("SOCKOPS: PASSIVE_ESTABLISHED lport=%u rport=%u cookie=%lx", 
			   lport, rport, cookie);
		bpf_sock_hash_update(ctx, &sock_map, &lport, BPF_ANY);
		break;
	case BPF_SOCK_OPS_STATE_CB:
		if (ctx->args[1] == BPF_TCP_CLOSE) {
			bpf_printk("SOCKOPS: TCP_CLOSE lport=%u", lport);
		}
		break;
	}

	return SK_PASS;
}