testing abstract unix domain socket address

abstract-addr.c

#include <stdio.h>
#include <sys/socket.h>
#include <sys/un.h>
#include <unistd.h>
#include <stdlib.h>

int create_abstract_socket(const char *name) {
  int sockfd = socket(AF_UNIX, SOCK_STREAM, 0);
  if (sockfd < 0) {
    return -1;
  }

  struct sockaddr_un addr;
  memset(&addr, 0, sizeof(addr));

  addr.sun_family = AF_UNIX;
  addr.sun_path[0] = '\0';

  strncpy(&addr.sun_path[1], name, sizeof(addr.sun_path) - 2);

  if (bind(sockfd, (struct sockaddr *)&addr, sizeof(addr)) < 0) {
    close(sockfd);
    return -1;
  }

  return sockfd;
}

int main(int argc, char *argv[]) {
  int server = 0;
  int opt;
  while ((opt = getopt(argc, argv, "s")) != -1) {
    switch (opt) {
      case 's':
        server = 1;
        break;
    }
  }

  char name[32];
  snprintf(name, sizeof(name), "%d", getpid());
  int sockfd = create_abstract_socket(name);

  if (server) {
    if (sockfd < 0 || listen(sockfd, 1) < 0) {
      exit(EXIT_FAILURE);
    }

    fprintf(stdout, "listening at %s\n", name);

    int fd;
    struct sockaddr_un addr;
    memset(&addr, 0, sizeof(addr));
    socklen_t addrlen = sizeof(addr);

    while ((fd = accept(sockfd, (struct sockaddr *)&addr, &addrlen)) > -1) {
      if (((struct sockaddr *)&addr)->sa_family != AF_UNIX) {
        fprintf(stderr, "unexpected socket type\n");
        exit(EXIT_FAILURE);
      }

      fprintf(stdout, "connected from %s%s\n",
              addr.sun_path[0] == '\0' ? "@" : "",
              addr.sun_path[0] == '\0' ? &addr.sun_path[1] : addr.sun_path);

      close(fd);
    }
  } else {
    struct sockaddr_un addr;
    memset(&addr, 0, sizeof(addr));

    addr.sun_family = AF_UNIX;
    addr.sun_path[0] = '\0';

    strncpy(&addr.sun_path[1], argv[optind], sizeof(addr.sun_path) - 2);

    fprintf(stdout, "%s is connecting to %s\n", name, argv[optind]);

    if (connect(sockfd, (const struct sockaddr *)&addr, sizeof(addr)) < 0) {
      exit(EXIT_FAILURE);
    }
  }

  exit(EXIT_SUCCESS);
}