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1// SPDX-License-Identifier: GPL-2.02// Copyright (c) 2018 Facebook3 4#include <linux/stddef.h>5#include <linux/bpf.h>6#include <sys/socket.h>7 8#include <bpf/bpf_helpers.h>9#include <bpf/bpf_endian.h>10 11#include <bpf_sockopt_helpers.h>12 13#define SRC1_IP4 0xAC100001U /* 172.16.0.1 */14#define SRC2_IP4 0x00000000U15#define SRC_REWRITE_IP4 0x7f000004U16#define DST_IP4 0xC0A801FEU /* 192.168.1.254 */17#define DST_REWRITE_IP4 0x7f000001U18#define DST_PORT 404019#define DST_REWRITE_PORT4 444420 21SEC("cgroup/sendmsg4")22int sendmsg_v4_prog(struct bpf_sock_addr *ctx)23{24 if (ctx->type != SOCK_DGRAM)25 return 0;26 27 if (!get_set_sk_priority(ctx))28 return 0;29 30 /* Rewrite source. */31 if (ctx->msg_src_ip4 == bpf_htonl(SRC1_IP4) ||32 ctx->msg_src_ip4 == bpf_htonl(SRC2_IP4)) {33 ctx->msg_src_ip4 = bpf_htonl(SRC_REWRITE_IP4);34 } else {35 /* Unexpected source. Reject sendmsg. */36 return 0;37 }38 39 /* Rewrite destination. */40 if ((ctx->user_ip4 >> 24) == (bpf_htonl(DST_IP4) >> 24) &&41 ctx->user_port == bpf_htons(DST_PORT)) {42 ctx->user_ip4 = bpf_htonl(DST_REWRITE_IP4);43 ctx->user_port = bpf_htons(DST_REWRITE_PORT4);44 } else {45 /* Unexpected source. Reject sendmsg. */46 return 0;47 }48 49 return 1;50}51 52SEC("cgroup/sendmsg4")53int sendmsg_v4_deny_prog(struct bpf_sock_addr *ctx)54{55 return 0;56}57 58char _license[] SEC("license") = "GPL";59