1bd4aed0eSJiong Wang // SPDX-License-Identifier: GPL-2.0 2bd4aed0eSJiong Wang // Copyright (c) 2018 Facebook 3bd4aed0eSJiong Wang 4bd4aed0eSJiong Wang #include <linux/stddef.h> 5bd4aed0eSJiong Wang #include <linux/bpf.h> 6bd4aed0eSJiong Wang #include <sys/socket.h> 7bd4aed0eSJiong Wang 83e689141SToke Høiland-Jørgensen #include <bpf/bpf_helpers.h> 93e689141SToke Høiland-Jørgensen #include <bpf/bpf_endian.h> 10bd4aed0eSJiong Wang 11*62476cc1SStanislav Fomichev #include <bpf_sockopt_helpers.h> 12*62476cc1SStanislav Fomichev 13bd4aed0eSJiong Wang #define SRC1_IP4 0xAC100001U /* 172.16.0.1 */ 14bd4aed0eSJiong Wang #define SRC2_IP4 0x00000000U 15bd4aed0eSJiong Wang #define SRC_REWRITE_IP4 0x7f000004U 16bd4aed0eSJiong Wang #define DST_IP4 0xC0A801FEU /* 192.168.1.254 */ 17bd4aed0eSJiong Wang #define DST_REWRITE_IP4 0x7f000001U 18bd4aed0eSJiong Wang #define DST_PORT 4040 19bd4aed0eSJiong Wang #define DST_REWRITE_PORT4 4444 20bd4aed0eSJiong Wang 21bd4aed0eSJiong Wang SEC("cgroup/sendmsg4") sendmsg_v4_prog(struct bpf_sock_addr * ctx)22bd4aed0eSJiong Wangint sendmsg_v4_prog(struct bpf_sock_addr *ctx) 23bd4aed0eSJiong Wang { 24bd4aed0eSJiong Wang if (ctx->type != SOCK_DGRAM) 25bd4aed0eSJiong Wang return 0; 26bd4aed0eSJiong Wang 27*62476cc1SStanislav Fomichev if (!get_set_sk_priority(ctx)) 28*62476cc1SStanislav Fomichev return 0; 29*62476cc1SStanislav Fomichev 30bd4aed0eSJiong Wang /* Rewrite source. */ 31bd4aed0eSJiong Wang if (ctx->msg_src_ip4 == bpf_htonl(SRC1_IP4) || 32bd4aed0eSJiong Wang ctx->msg_src_ip4 == bpf_htonl(SRC2_IP4)) { 33bd4aed0eSJiong Wang ctx->msg_src_ip4 = bpf_htonl(SRC_REWRITE_IP4); 34bd4aed0eSJiong Wang } else { 35bd4aed0eSJiong Wang /* Unexpected source. Reject sendmsg. */ 36bd4aed0eSJiong Wang return 0; 37bd4aed0eSJiong Wang } 38bd4aed0eSJiong Wang 39bd4aed0eSJiong Wang /* Rewrite destination. */ 40bd4aed0eSJiong Wang if ((ctx->user_ip4 >> 24) == (bpf_htonl(DST_IP4) >> 24) && 41bd4aed0eSJiong Wang ctx->user_port == bpf_htons(DST_PORT)) { 42bd4aed0eSJiong Wang ctx->user_ip4 = bpf_htonl(DST_REWRITE_IP4); 43bd4aed0eSJiong Wang ctx->user_port = bpf_htons(DST_REWRITE_PORT4); 44bd4aed0eSJiong Wang } else { 45bd4aed0eSJiong Wang /* Unexpected source. Reject sendmsg. */ 46bd4aed0eSJiong Wang return 0; 47bd4aed0eSJiong Wang } 48bd4aed0eSJiong Wang 49bd4aed0eSJiong Wang return 1; 50bd4aed0eSJiong Wang } 51bd4aed0eSJiong Wang 52bd4aed0eSJiong Wang char _license[] SEC("license") = "GPL"; 53