#include <linux/if_tun.h>
#include <assert.h>
+#include <array>
#include <atomic>
#include <chrono>
#include <thread>
}
#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)
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;
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;
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) {
static std::atomic<uint16_t> 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
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)
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
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,
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<sockaddr_in, std::array<unsigned char, PACKET_READ_SIZE + PACKET_READ_OFFS>, ssize_t> messagesPendingRingBuff[PENDING_MESSAGES_BUFF_SIZE];
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));
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;
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];
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);
}
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));
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
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));
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));
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]);
projects / tunudptotcp / blobdiff