X-Git-Url: http://git.bitcoin.ninja/index.cgi?a=blobdiff_plain;f=main.cpp;h=7c7cbed15fc503faf126d2f1cccafe06ca9acfb8;hb=HEAD;hp=c116e8994a27b53e6d0d3ec10a147b2704b26b73;hpb=340b163ec6af224bb7ed8cb7dced608621a4dd28;p=tunudptotcp diff --git a/main.cpp b/main.cpp index c116e89..7c7cbed 100644 --- a/main.cpp +++ b/main.cpp @@ -13,6 +13,7 @@ #include #include +#include #include #include #include @@ -186,8 +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 @@ -205,8 +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) @@ -223,16 +225,25 @@ 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; } static void build_ip_header(unsigned char* buf, struct pkt_hdr hdr, const in_addr_t& src_addr, const in_addr_t& dest_addr) { @@ -294,7 +305,7 @@ 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 (0x800) #define THREAD_POLL_SLEEP_MICS 250 @@ -363,16 +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]; @@ -399,9 +425,9 @@ 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)); @@ -511,10 +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 @@ -526,8 +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)); @@ -544,8 +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)); @@ -601,7 +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]);