net.c

#ifdef __linux__
#define _GNU_SOURCE
#endif

#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/un.h>
#include <unistd.h>

#ifdef __linux__
#include <bsd/bsd.h>
#endif

#include "net.h"
#include "util.h"

int voyeur_create_server_socket(struct sockaddr_un* sockinfo)
{
  // Configure a unix domain socket at a temporary path.
  char sockdir[] = "/tmp/libvoyeur-XXXXXXXXX";
  mkdtemp(sockdir);
  
  memset(sockinfo, 0, sizeof(struct sockaddr_un));
  sockinfo->sun_family = AF_UNIX;
  strlcpy(sockinfo->sun_path, sockdir, sizeof(sockinfo->sun_path));
  strlcat(sockinfo->sun_path, "/socket", sizeof(sockinfo->sun_path));
  unlink(sockinfo->sun_path);

  // Start the server.
  int server_sock = socket(AF_UNIX, SOCK_STREAM, 0);
  RETURN_ERROR_ON_FAIL(bind, server_sock, (struct sockaddr*) sockinfo,
                                          sizeof(struct sockaddr_un));
  RETURN_ERROR_ON_FAIL(listen, server_sock, 200);

  //chmod(sockinfo->sun_path, 0777);
  //fchmod(server_sock, 0777);

  fcntl(server_sock, F_SETFD, FD_CLOEXEC);
  return server_sock;
}

#define CONNECT_RETRIES 20
#define CONNECT_WAIT_MS 50
#define CONNECT_DEVIATION_MS 20

int voyeur_create_client_socket(const char* sockpath)
{
  struct sockaddr_un sockinfo;

  memset(&sockinfo, 0, sizeof(struct sockaddr_un));
  sockinfo.sun_family = AF_UNIX;
  strlcpy(sockinfo.sun_path, sockpath, sizeof(sockinfo.sun_path));

  // Connect to the server.
  int client_sock = socket(AF_UNIX, SOCK_STREAM, 0);
  int set = 1;

#ifdef __APPLE__
  setsockopt(client_sock, SOL_SOCKET, SO_NOSIGPIPE, (void *)&set, sizeof(int));
#endif

  unsigned try = 0;
  int connect_status = connect(client_sock,
                               (struct sockaddr*) &sockinfo,
                               sizeof(struct sockaddr_un));
  
  while (connect_status < 0 && ++try < CONNECT_RETRIES) {
    usleep(((CONNECT_WAIT_MS - CONNECT_DEVIATION_MS / 2) +
            arc4random_uniform(CONNECT_DEVIATION_MS)) * 1000);
    connect_status = connect(client_sock,
                             (struct sockaddr*) &sockinfo,
                             sizeof(struct sockaddr_un));
  }

  fcntl(client_sock, F_SETFD, FD_CLOEXEC);
  return client_sock;
}

void voyeur_close_socket(int fd)
{
  while (close(fd) < 0) {
    if (errno != EINTR) {
      // We really only want to keep spinning for EINTR.
      break;
    }
  }
}

#ifdef __linux__
#define SEND_OPTS MSG_NOSIGNAL
#else
#define SEND_OPTS 0
#endif

static int do_write(int fd, void* buf, size_t buf_size)
{
  ssize_t total_out = 0;
  while (total_out < (ssize_t) buf_size) {
    ssize_t out = send(fd,
                       buf + total_out,
                       buf_size - total_out,
                       SEND_OPTS);

    // Handle errors.
    if (out < 0) {
      if (errno == EAGAIN || errno == EWOULDBLOCK || errno == EINTR) {
        continue;
      } else {
        return -1;
      }
    }

    total_out += out;
  }

  return 0;
}

static int do_read(int fd, void* buf, size_t buf_size)
{
  ssize_t total_in = 0;
  while (total_in < (ssize_t) buf_size) {
    ssize_t in = read(fd,
                      buf + total_in,
                      buf_size - total_in);

    // Handle errors.
    if (in < 0) {
      if (errno == EAGAIN || errno == EINTR) {
        continue;
      } else {
        return -1;
      }
    }

    // Handle EOF.
    if (in == 0) {
      return -1;
    }

    total_in += in;
  }

  return 0;
}
  
int voyeur_write_msg_type(int fd, voyeur_msg_type val)
{
  return do_write(fd, (void*) &val, sizeof(voyeur_msg_type));
}

int voyeur_read_msg_type(int fd, voyeur_msg_type* val)
{
  return do_read(fd, (void*) val, sizeof(voyeur_msg_type));
}

int voyeur_write_event_type(int fd, voyeur_event_type val)
{
  return do_write(fd, (void*) &val, sizeof(voyeur_event_type));
}

int voyeur_read_event_type(int fd, voyeur_event_type* val)
{
  return do_read(fd, (void*) val, sizeof(voyeur_event_type));
}

int voyeur_write_byte(int fd, char val)
{
  return do_write(fd, (void*) &val, sizeof(char));
}

int voyeur_read_byte(int fd, char* val)
{
  return do_read(fd, (void*) val, sizeof(char));
}

int voyeur_write_int(int fd, int val)
{
  return do_write(fd, (void*) &val, sizeof(int));
}

int voyeur_read_int(int fd, int* val)
{
  return do_read(fd, (void*) val, sizeof(int));
}

int voyeur_write_size(int fd, size_t val)
{
  return do_write(fd, (void*) &val, sizeof(size_t));
}

int voyeur_read_size(int fd, size_t* val)
{
  return do_read(fd, (void*) val, sizeof(size_t));
}

int voyeur_write_pid(int fd, pid_t val)
{
  return do_write(fd, (void*) &val, sizeof(pid_t));
}

int voyeur_read_pid(int fd, pid_t* val)
{
  return do_read(fd, (void*) val, sizeof(pid_t));
}

int voyeur_write_string(int fd, const char* val, size_t len)
{
  if (val == NULL) {
    len = 0;
  } else if (len == 0) {
    len = strnlen(val, VOYEUR_MAX_STRLEN);
  }

  if (voyeur_write_size(fd, len) < 0) {
    return -1;
  }
  
  return do_write(fd, (void*) val, len);
}

int voyeur_read_string(int fd, char** val, size_t maxlen)
{
  size_t len;
  if (voyeur_read_size(fd, &len) < 0) {
    return -1;
  }

  if (maxlen == 0) {
    *val = malloc(len + 1);
  } else if (maxlen <= len) {
    SHOULD_NOT_REACH("libvoyeur: string buffer of size %zu "
                     "is too small for string of length %zu\n",
                     maxlen,
                     len);
    return -1;
  }
  
  if (do_read(fd, (void*) *val, len) < 0) {
    if (maxlen == 0) {
      free(*val);
    }
    return -1;
  }

  (*val)[len] = '\0';
  return 0;
}