// SPDX-License-Identifier: GPL-2.0 // Copyright (c) 2018 Facebook #include <string.h> #include <linux/stddef.h> #include <linux/bpf.h> #include <linux/in.h> #include <linux/in6.h> #include <sys/socket.h> #include "bpf_helpers.h" #include "bpf_endian.h" #define SRC_REWRITE_IP4 0x7f000004U #define DST_REWRITE_IP4 0x7f000001U #define DST_REWRITE_PORT4 4444 int _version SEC("version") = 1; SEC("cgroup/connect4") int connect_v4_prog(struct bpf_sock_addr *ctx) { struct bpf_sock_tuple tuple = {}; struct sockaddr_in sa; struct bpf_sock *sk; /* Verify that new destination is available. */ memset(&tuple.ipv4.saddr, 0, sizeof(tuple.ipv4.saddr)); memset(&tuple.ipv4.sport, 0, sizeof(tuple.ipv4.sport)); tuple.ipv4.daddr = bpf_htonl(DST_REWRITE_IP4); tuple.ipv4.dport = bpf_htons(DST_REWRITE_PORT4); if (ctx->type != SOCK_STREAM && ctx->type != SOCK_DGRAM) return 0; else if (ctx->type == SOCK_STREAM) sk = bpf_sk_lookup_tcp(ctx, &tuple, sizeof(tuple.ipv4), BPF_F_CURRENT_NETNS, 0); else sk = bpf_sk_lookup_udp(ctx, &tuple, sizeof(tuple.ipv4), BPF_F_CURRENT_NETNS, 0); if (!sk) return 0; if (sk->src_ip4 != tuple.ipv4.daddr || sk->src_port != DST_REWRITE_PORT4) { bpf_sk_release(sk); return 0; } bpf_sk_release(sk); /* Rewrite destination. */ ctx->user_ip4 = bpf_htonl(DST_REWRITE_IP4); ctx->user_port = bpf_htons(DST_REWRITE_PORT4); /* Rewrite source. */ memset(&sa, 0, sizeof(sa)); sa.sin_family = AF_INET; sa.sin_port = bpf_htons(0); sa.sin_addr.s_addr = bpf_htonl(SRC_REWRITE_IP4); if (bpf_bind(ctx, (struct sockaddr *)&sa, sizeof(sa)) != 0) return 0; return 1; } char _license[] SEC("license") = "GPL";