diff options
| -rw-r--r-- | README.md | 2 | ||||
| -rw-r--r-- | gre.c | 137 |
2 files changed, 107 insertions, 32 deletions
@@ -30,6 +30,8 @@ sudo ./gre <tun dev> remote local Copyright (C) 2015 - 2017, Xiaoxiao <i@pxx.io> +Copyright (C) 2019, Mikael Magnusson <mikma@users.sourceforge.net> + This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or @@ -2,6 +2,7 @@ * gre.c - userspace GRE tunnel * * Copyright (C) 2015 - 2017, Xiaoxiao <i@pxx.io> + * Copyright (C) 2019, Mikael Magnusson <mikma@users.sourceforge.net> * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by @@ -21,7 +22,9 @@ #include <errno.h> #include <fcntl.h> #include <linux/if_tun.h> +#include <net/ethernet.h> #include <net/if.h> +#include <netdb.h> #include <netinet/in.h> #include <pwd.h> #include <stdint.h> @@ -37,16 +40,21 @@ static int tun; static int sock; -static struct sockaddr_in remote; +static struct sockaddr_storage remote; +static size_t remote_len; uint8_t buf[4096]; static void gre_cb(void); +static void gre_ipv4(const uint8_t *buf, int n); +static void gre_ipv6(const uint8_t *buf, int n, const struct sockaddr_in6 *src); +static void gre_any(const uint8_t *buf, int n); static int tun_cb(void); static int tun_new(const char *dev); static int setnonblock(int fd); static int runas(const char *user); static int daemonize(void); +static int inet_addr_storage(const char *cp, struct sockaddr_storage *sp, size_t *sp_len); int main(int argc, char **argv) { @@ -65,35 +73,28 @@ int main(int argc, char **argv) return EXIT_FAILURE; } - sock = socket(AF_INET, SOCK_RAW, IPPROTO_GRE); - if (sock < 0) + struct sockaddr_storage local; + size_t local_len = 0; + if (inet_addr_storage(argv[3], &local, &local_len)) { - perror("socket"); + fprintf(stderr, "bad local address\n"); return EXIT_FAILURE; } - struct sockaddr_in local; - local.sin_family = AF_INET; - local.sin_port = htons(IPPROTO_GRE); - local.sin_addr.s_addr = inet_addr(argv[3]); - if (local.sin_addr.s_addr == INADDR_NONE) + sock = socket(local.ss_family, SOCK_RAW, IPPROTO_GRE); + if (sock < 0) { - fprintf(stderr, "bad local address\n"); + perror("socket"); return EXIT_FAILURE; } - else + + if (bind(sock, (struct sockaddr *)&local, local_len) != 0) { - if (bind(sock, (struct sockaddr *)&local, sizeof(local)) != 0) - { - perror("bind"); - return EXIT_FAILURE; - } + perror("bind"); + return EXIT_FAILURE; } - remote.sin_family = AF_INET; - remote.sin_port = htons(IPPROTO_GRE); - remote.sin_addr.s_addr = inet_addr(argv[2]); - if (remote.sin_addr.s_addr == INADDR_NONE) + if (inet_addr_storage(argv[2], &remote, &remote_len)) { fprintf(stderr, "bad remote address\n"); return EXIT_FAILURE; @@ -142,15 +143,28 @@ int main(int argc, char **argv) static void gre_cb(void) { - int ihl; // IP header length int n; + struct sockaddr_storage src; + size_t src_len = sizeof(src); - n = recv(sock, buf, sizeof(buf), 0); + memset(&src, 0, src_len); + n = recvfrom(sock, buf, sizeof(buf), 0, (struct sockaddr*)&src, &src_len); if (n < 0) { perror("recv"); return; } + + switch (remote.ss_family) { + case AF_INET: gre_ipv4(buf, n); break; + case AF_INET6: gre_ipv6(buf, n, (const struct sockaddr_in6*)&src); break; + } +} + +static void gre_ipv4(const uint8_t *buf, int n) +{ + int ihl; // IP header length + ihl = 4 * (buf[0] & 0x0f); if (ihl > 60 || ihl < 20) { @@ -158,30 +172,52 @@ static void gre_cb(void) return; } // check source IPv4 address - if (*(uint32_t *)(buf + 12) != remote.sin_addr.s_addr) + const struct sockaddr_in *remote_in = (const struct sockaddr_in *)&remote; + if (*(uint32_t *)(buf + 12) != remote_in->sin_addr.s_addr) { return; } + gre_any(buf + ihl, n - ihl); +} + +static void gre_ipv6(const uint8_t *buf, int n, const struct sockaddr_in6 *src) +{ + if (n < 40) + { + return; + } + // check source IPv6 address + const struct sockaddr_in6 *remote_in6 = (const struct sockaddr_in6 *)&remote; + if (memcmp(src->sin6_addr.s6_addr, remote_in6->sin6_addr.s6_addr, 16) != 0) + { + return; + } + + gre_any(buf, n); +} + +static void gre_any(const uint8_t *buf, int n) +{ // parse GRE header - if (*(uint16_t *)(buf + ihl) != 0) + if (*(uint16_t *)(buf) != 0) { return; } - uint16_t protocol = ntohs(*(uint16_t *)(buf + ihl + 2)); - if (protocol != 0x0800) + uint16_t protocol = ntohs(*(uint16_t *)(buf + 2)); + if (protocol != ETHERTYPE_IP && protocol != ETHERTYPE_IPV6) { return; } - write(tun, buf + ihl + 4, n - ihl - 4); + write(tun, buf, n); } static int tun_cb(void) { int n; - n = read(tun, buf + 4, sizeof(buf) - 4); + n = read(tun, buf, sizeof(buf)); if (n < 0) { int err = errno; @@ -191,9 +227,14 @@ static int tun_cb(void) return 0; } - *(uint16_t *)(buf) = 0; - *(uint16_t *)(buf + 2) = htons(0x0800); - sendto(sock, buf, n + 4, 0, (struct sockaddr *)&remote, sizeof(struct sockaddr)); + buf[0] = 0; + buf[1] = 0; + uint16_t proto = ntohs(*(uint16_t *)(buf + 2)); + if (proto != ETHERTYPE_IP && proto != ETHERTYPE_IPV6) + { + return 0; + } + sendto(sock, buf, n, 0, (struct sockaddr *)&remote, remote_len); return 0; } @@ -210,7 +251,7 @@ static int tun_new(const char *dev) bzero(&ifr, sizeof(struct ifreq)); - ifr.ifr_flags = IFF_TUN | IFF_NO_PI; + ifr.ifr_flags = IFF_TUN; if (*dev != '\0') { strncpy(ifr.ifr_name, dev, IFNAMSIZ); @@ -284,3 +325,35 @@ static int daemonize(void) return 0; } + +static int inet_addr_storage(const char *cp, struct sockaddr_storage *sp, size_t *sp_len) +{ + struct addrinfo hints; + struct addrinfo *result = NULL; + int res; + + memset(&hints, 0, sizeof(hints)); + hints.ai_family = AF_UNSPEC; + hints.ai_flags = AI_NUMERICHOST | AI_ADDRCONFIG; + res = getaddrinfo(cp, NULL, &hints, &result); + if (res != 0) { + fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(res)); + return -1; + } + + memcpy(sp, result->ai_addr, result->ai_addrlen); + *sp_len = result->ai_addrlen; + + freeaddrinfo(result); + result = NULL; + + if (sp->ss_family == AF_INET) { + struct sockaddr_in *sin = (struct sockaddr_in *)sp; + sin->sin_port = htons(IPPROTO_GRE); + } else if (sp->ss_family == AF_INET6) { + struct sockaddr_in6 *sin = (struct sockaddr_in6 *)sp; + sin->sin6_port = htons(IPPROTO_GRE); + } + + return 0; +} |