X-Git-Url: http://git.bitcoin.ninja/index.cgi?a=blobdiff_plain;f=main.cpp;h=7c7cbed15fc503faf126d2f1cccafe06ca9acfb8;hb=HEAD;hp=e070706ae7546eb945f95543592e271c00245c08;hpb=21295bd84d4089d71b5aa39af3325b1ceeaff99a;p=tunudptotcp diff --git a/main.cpp b/main.cpp index e070706..7c7cbed 100644 --- a/main.cpp +++ b/main.cpp @@ -13,6 +13,7 @@ #include #include +#include #include #include #include @@ -29,7 +30,19 @@ int getrandom(void* buf, size_t len, unsigned int flags) { } #endif -#define PACKET_READ_OFFS (20-16) +struct pkt_hdr { + // Note that ordering of the first three uint16_ts must match the wire! + uint16_t len; + uint16_t id; + uint16_t frag_flags: 3, + offset : 13; + uint8_t proto; + uint8_t padding; +}; +static_assert(sizeof(struct pkt_hdr) == 8); + +// Have to leave room to add a TCP header plus above header (after dropping IP header) +#define PACKET_READ_OFFS sizeof(pkt_hdr) #define PACKET_READ_SIZE (1500 - PACKET_READ_OFFS) static int tun_alloc(char *dev, const char* local_ip, const char* remote_ip, int queues, int *fds) @@ -62,7 +75,7 @@ static int tun_alloc(char *dev, const char* local_ip, const char* remote_ip, int fds[i] = fd; } - sprintf(buf, "ip link set %s mtu %d", dev, PACKET_READ_SIZE); + sprintf(buf, "ip link set dev %s mtu %ld", dev, PACKET_READ_SIZE - 20); err = system(buf); if (err) goto err; @@ -85,7 +98,7 @@ err: return err; } -static int check_ip_header(const unsigned char* buf, ssize_t buf_len, uint8_t expected_type) { +static int check_ip_header(const unsigned char* buf, ssize_t buf_len, int16_t expected_type, struct pkt_hdr *gen_hdr) { if (buf_len < 20) { // < size than IPv4? return -1; @@ -103,31 +116,23 @@ static int check_ip_header(const unsigned char* buf, ssize_t buf_len, uint8_t ex return -1; } - if ((((uint16_t)buf[2]) << 8 | buf[3]) != buf_len) { + /*if ((((uint16_t)buf[2]) << 8 | buf[3]) != buf_len) { //fprintf(stderr, "Packet len %u != %ld\n", ((uint16_t)buf[2]) << 8 | buf[3], buf_len); return -1; - } + }*/ - if (buf[9] != expected_type) { + if (expected_type > 0 && buf[9] != expected_type) { fprintf(stderr, "Packet type %u, not %u\n", buf[9], expected_type); return -1; } - return header_size; -} - -#define UDP_PORTS 4242 -static int check_udp_header(const unsigned char* buf, ssize_t buf_len) { - if (buf_len < 8) { - return -1; - } - if (((((uint16_t)buf[0]) << 8) | (buf[1])) != UDP_PORTS) { - return -1; - } - if (((((uint16_t)buf[2]) << 8) | (buf[3])) != UDP_PORTS) { - return -1; + if (gen_hdr) { + memcpy(gen_hdr, buf + 2, 6); // len, id, frag offset + gen_hdr->proto = buf[9]; + gen_hdr->padding = 0; } - return 8; + + return header_size; } void print_packet(const unsigned char* buf, ssize_t buf_len) { @@ -182,8 +187,9 @@ static std::atomic highest_recvd_seq(0), cur_seq(0); static std::atomic local_port(0); static uint16_t remote_port; static bool are_server; +static uint64_t timestamps_magic; -static void build_tcp_header(unsigned char* buf, uint32_t len, int syn, int synack, in_addr_t src_addr, in_addr_t dest_addr) { +static int build_tcp_header(unsigned char* buf, uint32_t len, int syn, int synack, in_addr_t src_addr, in_addr_t dest_addr) { buf[0 ] = local_port >> 8; // src port buf[1 ] = local_port; // src port buf[2 ] = remote_port >> 8; // dst port @@ -201,8 +207,8 @@ static void build_tcp_header(unsigned char* buf, uint32_t len, int syn, int syna buf[10] = their_seq >> (8 * 1); // ACK buf[11] = their_seq >> (8 * 0); // ACK - bool longpkt = syn || synack; - buf[12] = (longpkt ? 6 : 5) << 4; // data offset + unsigned char hdrlen = syn ? 36 : (synack ? 24 : 20); + buf[12] = (hdrlen/4) << 4; // data offset if (syn) buf[13] = 1 << 1; // SYN else if (synack) @@ -219,28 +225,33 @@ static void build_tcp_header(unsigned char* buf, uint32_t len, int syn, int syna buf[18] = 0x00; // URG Pointer buf[19] = 0x00; // URG Pointer - if (longpkt) { + if (syn || synack) { buf[20] = 0x01; // NOP buf[21] = 0x03; // Window Scale buf[22] = 0x03; // Window Scale Option Length buf[23] = 0x0e; // 1GB Window Size (0xffff << 0x0e) } + if (syn) { + buf[24] = 0x01; // NOP + buf[25] = 0x01; // NOP + buf[26] = 8; // Timestamp + buf[27] = 10; // Timestamp Option Length + memcpy(buf + 28, ×tamps_magic, 8); + } - uint16_t checksum = tcp_checksum(buf, len + 20 + (longpkt ? 4 : 0), src_addr, dest_addr); + uint16_t checksum = tcp_checksum(buf, len + hdrlen, src_addr, dest_addr); buf[16] = checksum; // Checksum buf[17] = checksum >> 8; // Checksum + + return hdrlen; } -// len is data length, not including headers! -static void build_ip_header(unsigned char* buf, uint16_t len, uint8_t proto, const in_addr_t& src_addr, const in_addr_t& dest_addr) { +static void build_ip_header(unsigned char* buf, struct pkt_hdr hdr, const in_addr_t& src_addr, const in_addr_t& dest_addr) { buf[0 ] = (4 << 4) | 5; // IPv4 + IHL of 5 (20 bytes) buf[1 ] = 0; // DSCP 0 + ECN 0 - buf[2 ] = (len + 20) >> 8; // Length - buf[3 ] = (len + 20); // Length - memset(buf + 4, 0, 4); // Identification and Fragment 0s - buf[6 ] = 1 << 6; // DF bit + memcpy(buf + 2, &hdr, 6); // length, identification, flags, and offset buf[8 ] = 255; // TTL - buf[9 ] = proto; // Protocol Number + buf[9 ] = hdr.proto; // Protocol Number buf[10] = 0; // Checksum buf[11] = 0; // Checksum @@ -252,21 +263,6 @@ static void build_ip_header(unsigned char* buf, uint16_t len, uint8_t proto, con buf[11] = checksum >> 8; } -// length is data length, not including headers -static void build_udp_header(unsigned char* buf, uint16_t len) { - buf[0] = UDP_PORTS >> 8; - buf[1] = UDP_PORTS & 0xff; - buf[2] = UDP_PORTS >> 8; - buf[3] = UDP_PORTS & 0xff; - buf[4] = (len + 8) >> 8; - buf[5] = (len + 8); - - // Checksum 0 for now - buf[6] = 0; - buf[7] = 0; -} - - const signed char p_util_hexdigit[256] = { -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1, -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1, @@ -309,11 +305,9 @@ static int fdr; static int fd[TUN_IF_COUNT]; static struct sockaddr_in dest; static in_addr_t src, tun_src, tun_dest; -static uint64_t tcp_init_magic; +static uint32_t starting_ack; -#define PENDING_MESSAGES_BUFF_SIZE (0x3000) -#define PACKET_READ_OFFS (20-16) -#define PACKET_READ_SIZE (1500 - PACKET_READ_OFFS) +#define PENDING_MESSAGES_BUFF_SIZE (0x800) #define THREAD_POLL_SLEEP_MICS 250 struct MessageQueue { std::tuple, ssize_t> messagesPendingRingBuff[PENDING_MESSAGES_BUFF_SIZE]; @@ -327,7 +321,7 @@ static MessageQueue tcp_to_tun_queue; static std::chrono::steady_clock::time_point last_ack_recv; static void tcp_to_tun() { - unsigned char buf[1500]; + unsigned char buf[PACKET_READ_SIZE + PACKET_READ_OFFS]; struct sockaddr_in pkt_src; memset(&pkt_src, 0, sizeof(pkt_src)); @@ -363,7 +357,7 @@ static void tcp_to_tun_queue_process() { unsigned char* buf = std::get<1>(msg).data(); ssize_t nread = std::get<2>(msg); - int header_size = check_ip_header(buf, nread, 0x06); // Only support TCP + int header_size = check_ip_header(buf, nread, 0x06, NULL); // Only support TCP if (header_size < 0) continue; @@ -380,16 +374,31 @@ static void tcp_to_tun_queue_process() { bool ack = tcp_buf[13] & (1 << 4); if (are_server && syn && !ack) { - // We're a server and just got a client - if (tcp_buf[4 ] != uint8_t(tcp_init_magic >> (7 * 8)) || - tcp_buf[5 ] != uint8_t(tcp_init_magic >> (6 * 8)) || - tcp_buf[6 ] != uint8_t(tcp_init_magic >> (5 * 8)) || - tcp_buf[7 ] != uint8_t(tcp_init_magic >> (4 * 8)) || - tcp_buf[8 ] != uint8_t(tcp_init_magic >> (3 * 8)) || - tcp_buf[9 ] != uint8_t(tcp_init_magic >> (2 * 8)) || - tcp_buf[10] != uint8_t(tcp_init_magic >> (1 * 8)) || - tcp_buf[11] != uint8_t(tcp_init_magic >> (0 * 8))) + uint32_t expected_ack = htobe32(starting_ack); + if (memcmp(tcp_buf + 8, &expected_ack, 4)) continue; + if (nread < 36 + header_size) { continue; } + // We're a server and just got a client...walk options until we find timestamps + const unsigned char* opt_buf = tcp_buf + 20; + bool found_magic = false; + while (!found_magic && opt_buf < buf + nread) { + switch (*opt_buf) { + case 1: opt_buf += 1; break; + case 2: opt_buf += 4; break; + case 3: opt_buf += 3; break; + // SACK should never appear + case 8: + if (opt_buf + 10 <= buf + nread) { + if (!memcmp(opt_buf + 2, ×tamps_magic, 8)) { + found_magic = true; + break; + } + } + // Fall through + default: opt_buf = buf + nread; + } + } + if (!found_magic) continue; fprintf(stderr, "Got SYN, sending SYNACK\n"); remote_port = (tcp_buf[0] << 8) | tcp_buf[1]; @@ -416,19 +425,21 @@ static void tcp_to_tun_queue_process() { last_ack_recv = std::chrono::steady_clock::now(); if (are_server && syn && !ack) { - build_tcp_header(tcp_buf, 0, 0, 1, src, dest.sin_addr.s_addr); + int len = build_tcp_header(tcp_buf, 0, 0, 1, src, dest.sin_addr.s_addr); - ssize_t res = sendto(fdr, tcp_buf, 20 + 4, 0, (struct sockaddr*)&dest, sizeof(dest)); + ssize_t res = sendto(fdr, tcp_buf, len, 0, (struct sockaddr*)&dest, sizeof(dest)); if (res < 0) { int err = errno; fprintf(stderr, "Failed to send SYNACK with err %d (%s)\n", err, strerror(err)); } } else if (!syn) { - tcp_buf += tcp_header_size - 20 - 8; // IPv4 header is 20 bytes + UDP header is 8 bytes + if (nread < (ssize_t)(tcp_header_size + header_size + sizeof(struct pkt_hdr))) continue; + struct pkt_hdr hdr; + memcpy(&hdr, tcp_buf + tcp_header_size, sizeof(struct pkt_hdr)); + tcp_buf += tcp_header_size + sizeof(struct pkt_hdr) - 20; // IPv4 header is 20 bytes - // Replace TCP with IPv4 header - build_udp_header(tcp_buf + 20, nread - tcp_header_size - header_size); - build_ip_header(tcp_buf, nread - tcp_header_size - header_size + 8, 0x11, tun_dest, tun_src); // UDP + // Replace TCP + pkt_hdr with IPv4 header + build_ip_header(tcp_buf, hdr, tun_dest, tun_src); write(fd[0], tcp_buf, nread - tcp_header_size - header_size + 20 + 8); } @@ -482,24 +493,26 @@ static void tun_to_tcp_queue_process() { unsigned char* buf = std::get<1>(msg).data(); ssize_t nread = std::get<2>(msg); - int header_size = check_ip_header(buf + PACKET_READ_OFFS, nread, 0x11); // Only support UDP - if (header_size < 0) + struct pkt_hdr hdr; + int header_size = check_ip_header(buf + PACKET_READ_OFFS, nread, -1, &hdr); // Any paket type is okay + if (header_size < 20) continue; - if (header_size + 8 > nread) { - fprintf(stderr, "Short UDP packet\n"); + if (header_size > nread) { + fprintf(stderr, "Short packet\n"); continue; } - if (check_udp_header(buf + PACKET_READ_OFFS + header_size, nread - header_size) != 8) { - fprintf(stderr, "Bad UDP header\n"); + if ((size_t)nread > 1500 - 20 - sizeof(struct pkt_hdr)) { // Packets must fit in 1500 bytes with a TCP and packet hdr + fprintf(stderr, "Long packet\n"); continue; } - unsigned char* tcp_start = buf + PACKET_READ_OFFS + header_size + 8 - 20; - build_tcp_header(tcp_start, nread - header_size - 8, 0, 0, src, dest.sin_addr.s_addr); + unsigned char* tcp_start = buf + PACKET_READ_OFFS + header_size - 20 - sizeof(struct pkt_hdr); + memcpy(tcp_start + 20, &hdr, sizeof(struct pkt_hdr)); + build_tcp_header(tcp_start, nread - header_size + sizeof(struct pkt_hdr), 0, 0, src, dest.sin_addr.s_addr); - ssize_t res = sendto(fdr, tcp_start, nread + 20 - 8 - header_size, 0, (struct sockaddr*)&dest, sizeof(dest)); + ssize_t res = sendto(fdr, tcp_start, nread + 20 + sizeof(struct pkt_hdr) - header_size, 0, (struct sockaddr*)&dest, sizeof(dest)); if (res < 0) { int err = errno; fprintf(stderr, "Failed to send with err %d (%s)\n", err, strerror(err)); @@ -524,10 +537,9 @@ int do_init() { local_port = local_port_tmp; } - uint32_t starting_ack = 0, starting_seq = 0; - memcpy(&starting_ack, &tcp_init_magic, 4); - memcpy(&starting_seq, ((const unsigned char*)&tcp_init_magic) + 4, 4); highest_recvd_seq = starting_ack; + uint32_t starting_seq; + assert(getrandom(&starting_seq, sizeof(starting_seq), 0) == sizeof(starting_seq)); cur_seq = starting_seq; if (!pause_tun_read_reinit_tcp) { // Not doing a re-init @@ -539,8 +551,8 @@ int do_init() { unsigned char buf[1500]; if (!are_server) { - build_tcp_header(buf, 0, 1, 0, src, dest.sin_addr.s_addr); - ssize_t res = sendto(fdr, buf, 20 + 4, 0, (struct sockaddr*)&dest, sizeof(dest)); + int len = build_tcp_header(buf, 0, 1, 0, src, dest.sin_addr.s_addr); + ssize_t res = sendto(fdr, buf, len, 0, (struct sockaddr*)&dest, sizeof(dest)); if (res < 0) { int err = errno; fprintf(stderr, "Failed to send initial SYN with err %d (%s)\n", err, strerror(err)); @@ -557,8 +569,8 @@ int do_init() { if (!are_server) { fprintf(stderr, "Got SYNACK, sending ACK and starting tun listen\n"); - build_tcp_header(buf, 0, 0, 0, src, dest.sin_addr.s_addr); - ssize_t res = sendto(fdr, buf, 20, 0, (struct sockaddr*)&dest, sizeof(dest)); + int len = build_tcp_header(buf, 0, 0, 0, src, dest.sin_addr.s_addr); + ssize_t res = sendto(fdr, buf, len, 0, (struct sockaddr*)&dest, sizeof(dest)); if (res < 0) { int err = errno; fprintf(stderr, "Failed to send initial ACK with err %d (%s)\n", err, strerror(err)); @@ -614,7 +626,9 @@ int main(int argc, char* argv[]) { remote_port = atoi(argv[4]); } - tcp_init_magic = atoll(argv[5]); + uint64_t tcp_init_magic = atoll(argv[5]); + starting_ack = tcp_init_magic >> 32; + timestamps_magic = htobe64(tcp_init_magic); src = inet_addr(argv[7]);