A wrapper for connecting and binding to TCP/UDP sockets

connection.c

#include <sys/types.h>
#include <sys/socket.h>
#include <netdb.h>
#include <string.h>
#include <assert.h>
#include <unistd.h>
#include <errno.h>
#include <ctype.h>
#include <stdio.h>

static int connection_addr(const char *addr, struct addrinfo **info, int server);

int connection_bind(const char *addr)
{
  struct addrinfo *info = NULL;
  int st = connection_addr(addr, &info, 1);
  if (st < 0) return st;

  int sock = socket(info->ai_family, info->ai_socktype, info->ai_protocol);
  if (sock < 0) {
    freeaddrinfo(info);
    return sock;
  }

  st = bind(sock, info->ai_addr, info->ai_addrlen);
  freeaddrinfo(info);
  if (st < 0) {
    close(sock);
    return st;
  }

  return sock;
}

int connection_connect(const char *addr)
{
  struct addrinfo *info = NULL;
  int st = connection_addr(addr, &info, 0);
  if (st < 0) return st;

  int sock = socket(info->ai_family, info->ai_socktype, info->ai_protocol);
  if (sock < 0) {
    freeaddrinfo(info);
    return sock;
  }

  st = connect(sock, info->ai_addr, info->ai_addrlen);
  freeaddrinfo(info);
  if (st < 0) {
    close(sock);
    return st;
  }

  return sock;
}

static int connection_addr(const char *addr, struct addrinfo **info, int server)
{
  // an addr is <type>://<host>:<port>
  const char *ptr = addr;
  int i, st;

  struct addrinfo hints;
  memset(&hints, 0, sizeof hints);

  if (strncasecmp(addr, "tcp://", strlen("tcp://")) == 0) {
    ptr += strlen("tcp://");
    hints.ai_family = AF_INET;
    hints.ai_socktype = SOCK_STREAM;
    hints.ai_protocol = IPPROTO_TCP;
  } else if (strncasecmp(addr, "udp://", strlen("udp://")) == 0) {
    ptr += strlen("udp://");
    hints.ai_family = AF_INET;
    hints.ai_socktype = SOCK_DGRAM;
    hints.ai_protocol = IPPROTO_UDP;
  } else {
    errno = ENOSYS;
    return -1;
  }

  char host[256];
  char port[16];

  for (i = 0; *ptr != ':' && *ptr != '\0' && i < sizeof(host); ++ptr, ++i) {
    host[i] = *ptr;
  }
  if (*ptr == '\0' || i == sizeof(host)) {
    errno = EINVAL;
    return -1;
  }
  ptr += 1; // skip the ':'
  host[i] = '\0';

  for (i = 0; *ptr != '\0' && isdigit(*ptr) && i < sizeof(port); ++ptr, ++i) {
    port[i] = *ptr;
  }
  if (i == sizeof(port)) {
    errno = EINVAL;
    return -1;
  }
  port[i] = '\0';

  st = getaddrinfo(host, port, &hints, info);
  if (st != 0) {
    errno = EINVAL;
    return -1;
  }

  if (server && host[0] == '\0') {
    // an empty host is returned as "localhost" when it should refer to all hosts when
    // binding to a server
    struct sockaddr_in *a = (struct sockaddr_in *)(*info)->ai_addr;
    a->sin_addr.s_addr = htonl(INADDR_ANY);
  }

  return 0;
}