tor_multipath_voip/src/packet.h

#pragma once
#include <assert.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <stdint.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <errno.h>
#include <netinet/in.h>
#include <arpa/inet.h>

/*
 * man 7 udp about receive operation on UDP sockets:
 *
 * > All  receive  operations  return only one packet.  When the packet is smaller than the passed
 * > buffer, only that much data is returned; when it is bigger, the packet is truncated  and  the
 * > MSG_TRUNC flag is set.  MSG_WAITALL is not supported.
 */

enum FD_STATE {
  FDS_READY,
  FDS_AGAIN,
  FDS_ERR
};

enum BP_MODE {
  BP_READING,
  BP_WRITING
};

enum PKT_CMD {
  CMD_HEALTH,
  CMD_CLEAR,
  CMD_XOR
};

union abstract_packet {
  char raw;
  struct {
    struct {
      uint16_t size;
      enum PKT_CMD cmd;
    } headers;

    union {
      struct {
        uint16_t id;
        uint8_t bitfield;
        uint8_t prevlink;
        uint16_t deltat;
        uint16_t min_blocked_pkt;
      } health;
      struct {
        uint16_t id;
        uint16_t port;
        char payload;
      } clear;
    } content;
  } fmt;
};

struct internet_packet {
  union abstract_packet ap;
  char rest[1499]; // MTU = 1500, 1 byte in the union as payload
};

struct buffer_packet {
  enum BP_MODE mode;
  uint8_t ap_count;
  uint16_t aread;
  uint16_t awrite;
  struct internet_packet ip;
};

struct udp_target {
  struct sockaddr_in addr;
  socklen_t addrlen;
  int set;
  int ref_count;
};

enum FD_STATE read_packet_from_tcp(int fd, struct buffer_packet* bp);
enum FD_STATE write_packet_to_tcp(int fd, struct buffer_packet* bp);
enum FD_STATE write_packet_to_udp(int fd, struct buffer_packet* bp, struct udp_target* udp_t);
enum FD_STATE read_packet_from_udp (int fd, struct buffer_packet* bp, struct udp_target* udp_t);