tools/testing/selftests/bpf/progs/sendmsg4_prog.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 // Copyright (c) 2018 Facebook
   3
   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                0x00000000U
  15 #define SRC_REWRITE_IP4         0x7f000004U
  16 #define DST_IP4                 0xC0A801FEU /* 192.168.1.254 */
  17 #define DST_REWRITE_IP4         0x7f000001U
  18 #define DST_PORT                4040
  19 #define DST_REWRITE_PORT4       4444
  20
  21 SEC("cgroup/sendmsg4")
  22 int 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
  52 char _license[] SEC("license") = "GPL";