// SPDX-License-Identifier: GPL-2.0
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#include <stdio.h>
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#include <assert.h>
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#include <unistd.h>
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#include <bpf/bpf.h>
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#include <bpf/libbpf.h>
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#include <sys/socket.h>
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#include <netinet/in.h>
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#include <arpa/inet.h>
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int main(int ac, char **argv)
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{
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struct sockaddr_in *serv_addr_in, *mapped_addr_in, *tmp_addr_in;
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struct sockaddr serv_addr, mapped_addr, tmp_addr;
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int serverfd, serverconnfd, clientfd, map_fd;
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struct bpf_link *link = NULL;
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struct bpf_program *prog;
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struct bpf_object *obj;
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socklen_t sockaddr_len;
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char filename[256];
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char *ip;
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serv_addr_in = (struct sockaddr_in *)&serv_addr;
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mapped_addr_in = (struct sockaddr_in *)&mapped_addr;
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tmp_addr_in = (struct sockaddr_in *)&tmp_addr;
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snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);
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obj = bpf_object__open_file(filename, NULL);
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if (libbpf_get_error(obj)) {
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fprintf(stderr, "ERROR: opening BPF object file failed\n");
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return 0;
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}
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prog = bpf_object__find_program_by_name(obj, "bpf_prog1");
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if (libbpf_get_error(prog)) {
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fprintf(stderr, "ERROR: finding a prog in obj file failed\n");
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goto cleanup;
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}
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/* load BPF program */
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if (bpf_object__load(obj)) {
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fprintf(stderr, "ERROR: loading BPF object file failed\n");
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goto cleanup;
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}
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map_fd = bpf_object__find_map_fd_by_name(obj, "dnat_map");
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if (map_fd < 0) {
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fprintf(stderr, "ERROR: finding a map in obj file failed\n");
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goto cleanup;
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}
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link = bpf_program__attach(prog);
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if (libbpf_get_error(link)) {
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fprintf(stderr, "ERROR: bpf_program__attach failed\n");
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link = NULL;
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goto cleanup;
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}
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assert((serverfd = socket(AF_INET, SOCK_STREAM, 0)) > 0);
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assert((clientfd = socket(AF_INET, SOCK_STREAM, 0)) > 0);
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/* Bind server to ephemeral port on lo */
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memset(&serv_addr, 0, sizeof(serv_addr));
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serv_addr_in->sin_family = AF_INET;
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serv_addr_in->sin_port = 0;
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serv_addr_in->sin_addr.s_addr = htonl(INADDR_LOOPBACK);
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assert(bind(serverfd, &serv_addr, sizeof(serv_addr)) == 0);
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sockaddr_len = sizeof(serv_addr);
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assert(getsockname(serverfd, &serv_addr, &sockaddr_len) == 0);
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ip = inet_ntoa(serv_addr_in->sin_addr);
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printf("Server bound to: %s:%d\n", ip, ntohs(serv_addr_in->sin_port));
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memset(&mapped_addr, 0, sizeof(mapped_addr));
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mapped_addr_in->sin_family = AF_INET;
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mapped_addr_in->sin_port = htons(5555);
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mapped_addr_in->sin_addr.s_addr = inet_addr("255.255.255.255");
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assert(!bpf_map_update_elem(map_fd, &mapped_addr, &serv_addr, BPF_ANY));
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assert(listen(serverfd, 5) == 0);
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ip = inet_ntoa(mapped_addr_in->sin_addr);
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printf("Client connecting to: %s:%d\n",
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ip, ntohs(mapped_addr_in->sin_port));
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assert(connect(clientfd, &mapped_addr, sizeof(mapped_addr)) == 0);
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sockaddr_len = sizeof(tmp_addr);
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ip = inet_ntoa(tmp_addr_in->sin_addr);
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assert((serverconnfd = accept(serverfd, &tmp_addr, &sockaddr_len)) > 0);
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printf("Server received connection from: %s:%d\n",
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ip, ntohs(tmp_addr_in->sin_port));
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sockaddr_len = sizeof(tmp_addr);
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assert(getpeername(clientfd, &tmp_addr, &sockaddr_len) == 0);
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ip = inet_ntoa(tmp_addr_in->sin_addr);
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printf("Client's peer address: %s:%d\n",
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ip, ntohs(tmp_addr_in->sin_port));
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/* Is the server's getsockname = the socket getpeername */
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assert(memcmp(&serv_addr, &tmp_addr, sizeof(struct sockaddr_in)) == 0);
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cleanup:
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bpf_link__destroy(link);
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bpf_object__close(obj);
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return 0;
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}
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