From: Matt Corallo Date: Wed, 16 Mar 2022 06:31:02 +0000 (+0000) Subject: Handle initial seq endianness correctly X-Git-Url: http://git.bitcoin.ninja/?a=commitdiff_plain;h=5aacce12cddca4ee3d49ba5eaca1945cc524d5ed;p=tunudptotcp Handle initial seq endianness correctly --- diff --git a/main.cpp b/main.cpp index c116e89..3fa3522 100644 --- a/main.cpp +++ b/main.cpp @@ -187,7 +187,7 @@ static std::atomic local_port(0); static uint16_t remote_port; static bool are_server; -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 @@ -233,6 +233,8 @@ static void build_tcp_header(unsigned char* buf, uint32_t len, int syn, int syna uint16_t checksum = tcp_checksum(buf, len + 20 + (longpkt ? 4 : 0), src_addr, dest_addr); buf[16] = checksum; // Checksum buf[17] = checksum >> 8; // Checksum + + return 20 + (longpkt ? 4 : 0); } 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 +296,7 @@ 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_seq, starting_ack; #define PENDING_MESSAGES_BUFF_SIZE (0x800) #define THREAD_POLL_SLEEP_MICS 250 @@ -363,15 +365,7 @@ 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))) + if (memcmp(tcp_buf + 4, &starting_seq, 4) || memcmp(tcp_buf + 8, &starting_ack, 4)) continue; fprintf(stderr, "Got SYN, sending SYNACK\n"); @@ -399,9 +393,9 @@ 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)); @@ -511,9 +505,6 @@ 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; cur_seq = starting_seq; @@ -526,8 +517,8 @@ 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 +535,8 @@ 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 +592,9 @@ 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_seq = htobe32(tcp_init_magic); + starting_ack = htobe32(tcp_init_magic >> 32); src = inet_addr(argv[7]);