path: root/src/src/ip.c

/* $Cambridge: exim/src/src/ip.c,v 1.8 2009/11/16 19:50:37 nm4 Exp $ */

/*************************************************
*     Exim - an Internet mail transport agent    *
*************************************************/

/* Copyright (c) University of Cambridge 1995 - 2009 */
/* See the file NOTICE for conditions of use and distribution. */

/* Functions for doing things with sockets. With the advent of IPv6 this has
got messier, so that it's worth pulling out the code into separate functions
that other parts of Exim can call, expecially as there are now several
different places in the code where sockets are used. */


#include "exim.h"


/*************************************************
*             Create a socket                    *
*************************************************/

/* Socket creation happens in a number of places so it's packaged here for
convenience.

Arguments:
  type       SOCK_DGRAM or SOCK_STREAM
  af         AF_INET or AF_INET6

Returns:     socket number or -1 on failure
*/

int
ip_socket(int type, int af)
{
int sock = socket(af, type, 0);
if (sock < 0)
  log_write(0, LOG_MAIN, "IPv%c socket creation failed: %s",
    (af == AF_INET6)? '6':'4', strerror(errno));
return sock;
}




#if HAVE_IPV6
/*************************************************
*      Convert printing address to numeric       *
*************************************************/

/* This function converts the textual form of an IP address into a numeric form
in an appropriate structure in an IPv6 environment. The getaddrinfo() function
can (apparently) handle more complicated addresses (e.g. those containing
scopes) than inet_pton() in some environments. We use hints to tell it that the
input must be a numeric address.

However, apparently some operating systems (or libraries) don't support
getaddrinfo(), so there is a build-time option to revert to inet_pton() (which
does not support scopes).

Arguments:
  address     textual form of the address
  addr        where to copy back the answer

Returns:      nothing - failure provokes a panic-die
*/

static void
ip_addrinfo(uschar *address, struct sockaddr_in6 *saddr)
{
#ifdef IPV6_USE_INET_PTON

  if (inet_pton(AF_INET6, CS address, &saddr->sin6_addr) != 1)
    log_write(0, LOG_MAIN|LOG_PANIC_DIE, "unable to parse \"%s\" as an "
      "IP address", address);
  saddr->sin6_family = AF_INET6;

#else

  int rc;
  struct addrinfo hints, *res;
  memset(&hints, 0, sizeof(hints));
  hints.ai_family = AF_INET6;
  hints.ai_socktype = SOCK_STREAM;
  hints.ai_flags = AI_NUMERICHOST;
  if ((rc = getaddrinfo(CS address, NULL, &hints, &res)) != 0 || res == NULL)
    log_write(0, LOG_MAIN|LOG_PANIC_DIE, "unable to parse \"%s\" as an "
      "IP address: %s", address,
      (rc == 0)? "NULL result returned" : gai_strerror(rc));
  memcpy(saddr, res->ai_addr, res->ai_addrlen);
  freeaddrinfo(res);

#endif
}
#endif  /* HAVE_IPV6 */


/*************************************************
*         Bind socket to interface and port      *
*************************************************/

/* This function binds a socket to a local interface address and port. For a
wildcard IPv6 bind, the address is ":".

Arguments:
  sock           the socket
  af             AF_INET or AF_INET6 - the socket type
  address        the IP address, in text form
  port           the IP port (host order)

Returns:         the result of bind()
*/

int
ip_bind(int sock, int af, uschar *address, int port)
{
int s_len;
union sockaddr_46 sin;
memset(&sin, 0, sizeof(sin));

/* Setup code when using an IPv6 socket. The wildcard address is ":", to
ensure an IPv6 socket is used. */

#if HAVE_IPV6
if (af == AF_INET6)
  {
  if (address[0] == ':' && address[1] == 0)
    {
    sin.v6.sin6_family = AF_INET6;
    sin.v6.sin6_addr = in6addr_any;
    }
  else
    {
    ip_addrinfo(address, &sin.v6);  /* Panic-dies on error */
    }
  sin.v6.sin6_port = htons(port);
  s_len = sizeof(sin.v6);
  }
else
#else     /* HAVE_IPv6 */
af = af;  /* Avoid compiler warning */
#endif    /* HAVE_IPV6 */

/* Setup code when using IPv4 socket. The wildcard address is "". */

  {
  sin.v4.sin_family = AF_INET;
  sin.v4.sin_port = htons(port);
  s_len = sizeof(sin.v4);
  if (address[0] == 0)
    sin.v4.sin_addr.s_addr = (S_ADDR_TYPE)INADDR_ANY;
  else
    sin.v4.sin_addr.s_addr = (S_ADDR_TYPE)inet_addr(CS address);
  }

/* Now we can call the bind() function */

return bind(sock, (struct sockaddr *)&sin, s_len);
}



/*************************************************
*        Connect socket to remote host           *
*************************************************/

/* This function connects a socket to a remote address and port. The socket may
or may not have previously been bound to a local interface. The socket is not
closed, even in cases of error. It is expected that the calling function, which
created the socket, will be the one that closes it.

Arguments:
  sock        the socket
  af          AF_INET6 or AF_INET for the socket type
  address     the remote address, in text form
  port        the remote port
  timeout     a timeout

Returns:      0 on success; -1 on failure, with errno set
*/

int
ip_connect(int sock, int af, uschar *address, int port, int timeout)
{
struct sockaddr_in s_in4;
struct sockaddr *s_ptr;
int s_len, rc, save_errno;

/* For an IPv6 address, use an IPv6 sockaddr structure. */

#if HAVE_IPV6
struct sockaddr_in6 s_in6;
if (af == AF_INET6)
  {
  memset(&s_in6, 0, sizeof(s_in6));
  ip_addrinfo(address, &s_in6);   /* Panic-dies on error */
  s_in6.sin6_port = htons(port);
  s_ptr = (struct sockaddr *)&s_in6;
  s_len = sizeof(s_in6);
  }
else
#else     /* HAVE_IPV6 */
af = af;  /* Avoid compiler warning */
#endif    /* HAVE_IPV6 */

/* For an IPv4 address, use an IPv4 sockaddr structure, even on a system with
IPv6 support. */

  {
  memset(&s_in4, 0, sizeof(s_in4));
  s_in4.sin_family = AF_INET;
  s_in4.sin_port = htons(port);
  s_in4.sin_addr.s_addr = (S_ADDR_TYPE)inet_addr(CS address);
  s_ptr = (struct sockaddr *)&s_in4;
  s_len = sizeof(s_in4);
  }

/* If no connection timeout is set, just call connect() without setting a
timer, thereby allowing the inbuilt OS timeout to operate. */

sigalrm_seen = FALSE;
if (timeout > 0) alarm(timeout);
rc = connect(sock, s_ptr, s_len);
save_errno = errno;
alarm(0);

/* There is a testing facility for simulating a connection timeout, as I
can't think of any other way of doing this. It converts a connection refused
into a timeout if the timeout is set to 999999. */

if (running_in_test_harness)
  {
  if (save_errno == ECONNREFUSED && timeout == 999999)
    {
    rc = -1;
    save_errno = EINTR;
    sigalrm_seen = TRUE;
    }
  }

/* Success */

if (rc >= 0) return 0;

/* A failure whose error code is "Interrupted system call" is in fact
an externally applied timeout if the signal handler has been run. */

errno = (save_errno == EINTR && sigalrm_seen)? ETIMEDOUT : save_errno;
return -1;
}



/*************************************************
*         Set keepalive on a socket              *
*************************************************/

/* Can be called for both incoming and outgoing sockets.

Arguments:
  sock       the socket
  address    the remote host address, for failure logging
  torf       true for outgoing connection, false for incoming

Returns:     nothing
*/

void
ip_keepalive(int sock, uschar *address, BOOL torf)
{
int fodder = 1;
if (setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE,
    (uschar *)(&fodder), sizeof(fodder)) != 0)
  log_write(0, LOG_MAIN, "setsockopt(SO_KEEPALIVE) on connection %s %s "
    "failed: %s", torf? "to":"from", address, strerror(errno));
}



/*************************************************
*         Receive from a socket with timeout     *
*************************************************/

/* The timeout is implemented using select(), and we loop to cover select()
getting interrupted, and the possibility of select() returning with a positive
result but no ready descriptor. Is this in fact possible?

Arguments:
  sock        the socket
  buffer      to read into
  bufsize     the buffer size
  timeout     the timeout

Returns:      > 0 => that much data read
              <= 0 on error or EOF; errno set - zero for EOF
*/

int
ip_recv(int sock, uschar *buffer, int buffsize, int timeout)
{
fd_set select_inset;
struct timeval tv;
int start_recv = time(NULL);
int rc;

/* Wait until the socket is ready */

for (;;)
  {
  FD_ZERO (&select_inset);
  FD_SET (sock, &select_inset);
  tv.tv_sec = timeout;
  tv.tv_usec = 0;

  DEBUG(D_transport) debug_printf("waiting for data on socket\n");
  rc = select(sock + 1, (SELECT_ARG2_TYPE *)&select_inset, NULL, NULL, &tv);

  /* If some interrupt arrived, just retry. We presume this to be rare,
  but it can happen (e.g. the SIGUSR1 signal sent by exiwhat causes
  select() to exit).

  Aug 2004: Somebody set up a cron job that ran exiwhat every 2 minutes, making
  the interrupt not at all rare. Since the timeout is typically more than 2
  minutes, the effect was to block the timeout completely. To prevent this
  happening again, we do an explicit time test. */

  if (rc < 0 && errno == EINTR)
    {
    DEBUG(D_transport) debug_printf("EINTR while waiting for socket data\n");
    if (time(NULL) - start_recv < timeout) continue;
    DEBUG(D_transport) debug_printf("total wait time exceeds timeout\n");
    }

  /* Handle a timeout, and treat any other select error as a timeout, including
  an EINTR when we have been in this loop for longer than timeout. */

  if (rc <= 0)
    {
    errno = ETIMEDOUT;
    return -1;
    }

  /* If the socket is ready, break out of the loop. */

  if (FD_ISSET(sock, &select_inset)) break;
  }

/* The socket is ready, read from it (via TLS if it's active). On EOF (i.e.
close down of the connection), set errno to zero; otherwise leave it alone. */

#ifdef SUPPORT_TLS
if (tls_active == sock)
  rc = tls_read(buffer, buffsize);
else
#endif
  rc = recv(sock, buffer, buffsize, 0);

if (rc > 0) return rc;
if (rc == 0) errno = 0;
return -1;
}


/* End of ip.c */