X-Git-Url: https://git.exim.org/exim.git/blobdiff_plain/bb7b9411e1b4f95418bed7b35035186e261063a6..568dbf1701e031eb1b0cfb50d3a656477f4198c8:/src/src/ip.c

diff --git a/src/src/ip.c b/src/src/ip.c
index d6e4e7ad8..aa42343fb 100644
--- a/src/src/ip.c
+++ b/src/src/ip.c
@@ -2,18 +2,25 @@
 *     Exim - an Internet mail transport agent    *
 *************************************************/
 
-/* Copyright (c) University of Cambridge 1995 - 2013 */
+/* Copyright (c) University of Cambridge 1995 - 2018 */
+/* Copyright (c) The Exim Maintainers 2020 - 2021 */
 /* 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
+that other parts of Exim can call, especially as there are now several
 different places in the code where sockets are used. */
 
 
 #include "exim.h"
 
 
+#if defined(TCP_FASTOPEN)
+# if defined(MSG_FASTOPEN) || defined(EXIM_TFO_CONNECTX) || defined(EXIM_TFO_FREEBSD)
+#  define EXIM_SUPPORT_TFO
+# endif
+#endif
+
 /*************************************************
 *             Create a socket                    *
 *************************************************/
@@ -64,11 +71,11 @@ Returns:      nothing - failure provokes a panic-die
 */
 
 static void
-ip_addrinfo(uschar *address, struct sockaddr_in6 *saddr)
+ip_addrinfo(const uschar *address, struct sockaddr_in6 *saddr)
 {
 #ifdef IPV6_USE_INET_PTON
 
-  if (inet_pton(AF_INET6, CS address, &saddr->sin6_addr) != 1)
+  if (inet_pton(AF_INET6, CCS 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;
@@ -81,7 +88,7 @@ ip_addrinfo(uschar *address, struct sockaddr_in6 *saddr)
   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)
+  if ((rc = getaddrinfo(CCS 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));
@@ -97,24 +104,11 @@ ip_addrinfo(uschar *address, struct sockaddr_in6 *saddr)
 *         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)
+ip_addr(void * sin_, int af, const uschar * address, int port)
 {
-int s_len;
-union sockaddr_46 sin;
-memset(&sin, 0, sizeof(sin));
+union sockaddr_46 * sin = sin_;
+memset(sin, 0, sizeof(*sin));
 
 /* Setup code when using an IPv6 socket. The wildcard address is ":", to
 ensure an IPv6 socket is used. */
@@ -124,35 +118,48 @@ if (af == AF_INET6)
   {
   if (address[0] == ':' && address[1] == 0)
     {
-    sin.v6.sin6_family = AF_INET6;
-    sin.v6.sin6_addr = in6addr_any;
+    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);
+    ip_addrinfo(address, &sin->v6);  /* Panic-dies on error */
+  sin->v6.sin6_port = htons(port);
+  return 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);
+  sin->v4.sin_family = AF_INET;
+  sin->v4.sin_port = htons(port);
+  sin->v4.sin_addr.s_addr = address[0] == 0
+    ? (S_ADDR_TYPE)INADDR_ANY
+    : (S_ADDR_TYPE)inet_addr(CS address);
+  return sizeof(sin->v4);
   }
+}
+
+
+
+/* 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)
 
-/* Now we can call the bind() function */
+Returns:         the result of bind()
+*/
 
+int
+ip_bind(int sock, int af, uschar *address, int port)
+{
+union sockaddr_46 sin;
+int s_len = ip_addr(&sin, af, address, port);
 return bind(sock, (struct sockaddr *)&sin, s_len);
 }
 
@@ -172,13 +179,16 @@ Arguments:
   af          AF_INET6 or AF_INET for the socket type
   address     the remote address, in text form
   port        the remote port
-  timeout     a timeout
+  timeout     a timeout (zero for indefinite timeout)
+  fastopen_blob    non-null iff TCP_FASTOPEN can be used; may indicate early-data to
+		be sent in SYN segment.  Any such data must be idempotent.
 
 Returns:      0 on success; -1 on failure, with errno set
 */
 
 int
-ip_connect(int sock, int af, uschar *address, int port, int timeout)
+ip_connect(int sock, int af, const uschar *address, int port, int timeout,
+  const blob * fastopen_blob)
 {
 struct sockaddr_in s_in4;
 struct sockaddr *s_ptr;
@@ -197,8 +207,6 @@ if (af == AF_INET6)
   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
@@ -208,7 +216,7 @@ 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_in4.sin_addr.s_addr = (S_ADDR_TYPE)inet_addr(CCS address);
   s_ptr = (struct sockaddr *)&s_in4;
   s_len = sizeof(s_in4);
   }
@@ -216,39 +224,331 @@ IPv6 support. */
 /* If no connection timeout is set, just call connect() without setting a
 timer, thereby allowing the inbuilt OS timeout to operate. */
 
+callout_address = string_sprintf("[%s]:%d", address, port);
 sigalrm_seen = FALSE;
-if (timeout > 0) alarm(timeout);
-rc = connect(sock, s_ptr, s_len);
+if (timeout > 0) ALARM(timeout);
+
+#ifdef EXIM_SUPPORT_TFO
+/* TCP Fast Open, if the system has a cookie from a previous call to
+this peer, can send data in the SYN packet.  The peer can send data
+before it gets our ACK of its SYN,ACK - the latter is useful for
+the SMTP banner.  Other (than SMTP) cases of TCP connections can
+possibly use the data-on-syn, so support that too. */
+
+if (fastopen_blob && f.tcp_fastopen_ok)
+  {
+# ifdef MSG_FASTOPEN
+  /* This is a Linux implementation. */
+
+  if ((rc = sendto(sock, fastopen_blob->data, fastopen_blob->len,
+		    MSG_FASTOPEN | MSG_DONTWAIT, s_ptr, s_len)) >= 0)
+	/* seen for with-data, experimental TFO option, with-cookie case */
+	/* seen for with-data, proper TFO opt, with-cookie case */
+    {
+    DEBUG(D_transport|D_v)
+      debug_printf(" TFO mode connection attempt to %s, %lu data\n",
+	address, (unsigned long)fastopen_blob->len);
+    /*XXX also seen on successful TFO, sigh */
+    tcp_out_fastopen = fastopen_blob->len > 0 ?  TFO_ATTEMPTED_DATA : TFO_ATTEMPTED_NODATA;
+    }
+  else switch (errno)
+    {
+    case EINPROGRESS:	/* expected if we had no cookie for peer */
+	/* seen for no-data, proper TFO option, both cookie-request and with-cookie cases */
+	/*  apparently no visibility of the diffference at this point */
+	/* seen for with-data, proper TFO opt, cookie-req */
+	/*   with netwk delay, post-conn tcp_info sees unacked 1 for R, 2 for C; code in smtp_out.c */
+	/* ? older Experimental TFO option behaviour ? */
+      DEBUG(D_transport|D_v) debug_printf(" TFO mode sendto, %s data: EINPROGRESS\n",
+	fastopen_blob->len > 0 ? "with"  : "no");
+      if (!fastopen_blob->data)
+	{
+	tcp_out_fastopen = TFO_ATTEMPTED_NODATA;		/* we tried; unknown if useful yet */
+	rc = 0;
+	}
+      else					/* queue unsent data */
+	rc = send(sock, fastopen_blob->data, fastopen_blob->len, 0);
+      break;
+
+    case EOPNOTSUPP:
+      DEBUG(D_transport)
+	debug_printf("Tried TCP Fast Open but apparently not enabled by sysctl\n");
+      goto legacy_connect;
+
+    case EPIPE:
+      DEBUG(D_transport)
+	debug_printf("Tried TCP Fast Open but kernel too old to support it\n");
+      goto legacy_connect;
+    }
+
+# elif defined(EXIM_TFO_FREEBSD)
+  /* Re: https://people.freebsd.org/~pkelsey/tfo-tools/tfo-client.c */
+
+  if (setsockopt(sock, IPPROTO_TCP, TCP_FASTOPEN, &on, sizeof(on)) < 0)
+    {
+    DEBUG(D_transport)
+      debug_printf("Tried TCP Fast Open but apparently not enabled by sysctl\n");
+    goto legacy_connect;
+    }
+  if ((rc = sendto(sock, fastopen_blob->data, fastopen_blob->len, 0,
+		    s_ptr, s_len)) >= 0)
+    {
+    DEBUG(D_transport|D_v)
+      debug_printf(" TFO mode connection attempt to %s, %lu data\n",
+	address, (unsigned long)fastopen_blob->len);
+    tcp_out_fastopen = fastopen_blob->len > 0 ?  TFO_ATTEMPTED_DATA : TFO_ATTEMPTED_NODATA;
+    }
+
+# elif defined(EXIM_TFO_CONNECTX)
+  /* MacOS */
+  sa_endpoints_t ends = {
+    .sae_srcif = 0, .sae_srcaddr = NULL, .sae_srcaddrlen = 0,
+    .sae_dstaddr = s_ptr, .sae_dstaddrlen = s_len };
+  struct iovec iov = {
+    .iov_base = fastopen_blob->data, .iov_len = fastopen_blob->len };
+  size_t len;
+
+  if ((rc = connectx(sock, &ends, SAE_ASSOCID_ANY,
+	     CONNECT_DATA_IDEMPOTENT, &iov, 1, &len, NULL)) == 0)
+    {
+    DEBUG(D_transport|D_v)
+      debug_printf(" TFO mode connection attempt to %s, %lu data\n",
+	address, (unsigned long)fastopen_blob->len);
+    tcp_out_fastopen = fastopen_blob->len > 0 ?  TFO_ATTEMPTED_DATA : TFO_ATTEMPTED_NODATA;
+
+    if (len != fastopen_blob->len)
+      DEBUG(D_transport|D_v)
+	debug_printf(" only queued %lu data!\n", (unsigned long)len);
+    }
+  else if (errno == EINPROGRESS)
+    {
+    DEBUG(D_transport|D_v) debug_printf(" TFO mode connectx, %s data: EINPROGRESS\n",
+      fastopen_blob->len > 0 ? "with"  : "no");
+    if (!fastopen_blob->data)
+      {
+      tcp_out_fastopen = TFO_ATTEMPTED_NODATA;		/* we tried; unknown if useful yet */
+      rc = 0;
+      }
+    else	/* assume that no data was queued; block in send */
+      rc = send(sock, fastopen_blob->data, fastopen_blob->len, 0);
+    }
+# endif
+  }
+else
+#endif	/*EXIM_SUPPORT_TFO*/
+  {
+#if defined(EXIM_SUPPORT_TFO) && !defined(EXIM_TFO_CONNECTX)
+legacy_connect:
+#endif
+
+  DEBUG(D_transport|D_v) if (fastopen_blob)
+    debug_printf(" non-TFO mode connection attempt to %s, %lu data\n",
+      address, (unsigned long)fastopen_blob->len);
+  if ((rc = connect(sock, s_ptr, s_len)) >= 0)
+    if (  fastopen_blob && fastopen_blob->data && fastopen_blob->len
+       && send(sock, fastopen_blob->data, fastopen_blob->len, 0) < 0)
+	rc = -1;
+  }
+
 save_errno = errno;
-alarm(0);
+ALARM_CLR(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 (f.running_in_test_harness  && save_errno == ECONNREFUSED && timeout == 999999)
   {
-  if (save_errno == ECONNREFUSED && timeout == 999999)
-    {
-    rc = -1;
-    save_errno = EINTR;
-    sigalrm_seen = TRUE;
-    }
+  rc = -1;
+  save_errno = EINTR;
+  sigalrm_seen = TRUE;
   }
 
 /* Success */
 
-if (rc >= 0) return 0;
+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;
+errno = save_errno == EINTR && sigalrm_seen ? ETIMEDOUT : save_errno;
 return -1;
 }
 
 
 
+/*************************************************
+*    Create connected socket to remote host      *
+*************************************************/
+
+/* Create a socket and connect to host (name or number, ipv6 ok)
+   at one of port-range.
+
+Arguments:
+  type          SOCK_DGRAM or SOCK_STREAM
+  af            AF_INET6 or AF_INET for the socket type
+  hostname	host name, or ip address (as text)
+  portlo,porthi the remote port range
+  timeout       a timeout
+  connhost	if not NULL, host_item to be filled in with connection details
+  errstr        pointer for allocated string on error
+  fastopen_blob	with SOCK_STREAM, if non-null, request TCP Fast Open.
+		Additionally, optional idempotent early-data to send
+
+Return:
+  socket fd, or -1 on failure (having allocated an error string)
+*/
+int
+ip_connectedsocket(int type, const uschar * hostname, int portlo, int porthi,
+      int timeout, host_item * connhost, uschar ** errstr, const blob * fastopen_blob)
+{
+int namelen;
+host_item shost;
+int af = 0, fd, fd4 = -1, fd6 = -1;
+
+shost.next = NULL;
+shost.address = NULL;
+shost.port = portlo;
+shost.mx = -1;
+
+namelen = Ustrlen(hostname);
+
+/* Anything enclosed in [] must be an IP address. */
+
+if (hostname[0] == '[' &&
+    hostname[namelen - 1] == ']')
+  {
+  uschar * host = string_copyn(hostname+1, namelen-2);
+  if (string_is_ip_address(host, NULL) == 0)
+    {
+    *errstr = string_sprintf("malformed IP address \"%s\"", hostname);
+    return -1;
+    }
+  shost.name = shost.address = host;
+  }
+
+/* Otherwise check for an unadorned IP address */
+
+else if (string_is_ip_address(hostname, NULL) != 0)
+  shost.name = shost.address = string_copyn(hostname, namelen);
+
+/* Otherwise lookup IP address(es) from the name */
+
+else
+  {
+  shost.name = string_copyn(hostname, namelen);
+  if (host_find_byname(&shost, NULL, HOST_FIND_QUALIFY_SINGLE,
+      NULL, FALSE) != HOST_FOUND)
+    {
+    *errstr = string_sprintf("no IP address found for host %s", shost.name);
+    return -1;
+    }
+  }
+
+/* Try to connect to the server - test each IP till one works */
+
+for (host_item * h = &shost; h; h = h->next)
+  {
+  fd = Ustrchr(h->address, ':') != 0
+    ? fd6 < 0 ? (fd6 = ip_socket(type, af = AF_INET6)) : fd6
+    : fd4 < 0 ? (fd4 = ip_socket(type, af = AF_INET )) : fd4;
+
+  if (fd < 0)
+    {
+    *errstr = string_sprintf("failed to create socket: %s", strerror(errno));
+    goto bad;
+    }
+
+  for (int port = portlo; port <= porthi; port++)
+    if (ip_connect(fd, af, h->address, port, timeout, fastopen_blob) == 0)
+      {
+      if (fd6 >= 0 && fd != fd6) close(fd6);
+      if (fd4 >= 0 && fd != fd4) close(fd4);
+      if (connhost)
+	{
+	h->port = port;
+	*connhost = *h;
+	connhost->next = NULL;
+	}
+      return fd;
+      }
+  }
+
+*errstr = string_sprintf("failed to connect to any address for %s: %s",
+  hostname, strerror(errno));
+
+bad:
+  close(fd4); close(fd6); return -1;
+}
+
+
+/*XXX TFO? */
+int
+ip_tcpsocket(const uschar * hostport, uschar ** errstr, int tmo,
+  host_item * connhost)
+{
+int scan;
+uschar hostname[256];
+unsigned int portlow, porthigh;
+
+/* extract host and port part */
+scan = sscanf(CS hostport, "%255s %u-%u", hostname, &portlow, &porthigh);
+if (scan != 3)
+  {
+  if (scan != 2)
+    {
+    *errstr = string_sprintf("invalid socket '%s'", hostport);
+    return -1;
+    }
+  porthigh = portlow;
+  }
+
+return ip_connectedsocket(SOCK_STREAM, hostname, portlow, porthigh,
+			  tmo, connhost, errstr, NULL);
+}
+
+int
+ip_unixsocket(const uschar * path, uschar ** errstr)
+{
+int sock;
+struct sockaddr_un server;
+
+if ((sock = socket(AF_UNIX, SOCK_STREAM, 0)) < 0)
+  {
+  *errstr = US"can't open UNIX socket.";
+  return -1;
+  }
+
+callout_address = string_copy(path);
+server.sun_family = AF_UNIX;
+Ustrncpy(US server.sun_path, path, sizeof(server.sun_path)-1);
+server.sun_path[sizeof(server.sun_path)-1] = '\0';
+if (connect(sock, (struct sockaddr *) &server, sizeof(server)) < 0)
+  {
+  int err = errno;
+  (void)close(sock);
+  *errstr = string_sprintf("unable to connect to UNIX socket (%s): %s",
+		path, strerror(err));
+  return -1;
+  }
+return sock;
+}
+
+/* spec is either an absolute path (with a leading /), or
+a host (name or IP) and port (whitespace-separated).
+The port can be a range, dash-separated, or a single number.
+
+For a TCP socket, optionally fill in a  host_item.
+*/
+int
+ip_streamsocket(const uschar * spec, uschar ** errstr, int tmo,
+  host_item * connhost)
+{
+return *spec == '/'
+  ? ip_unixsocket(spec, errstr) : ip_tcpsocket(spec, errstr, tmo, connhost);
+}
+
 /*************************************************
 *         Set keepalive on a socket              *
 *************************************************/
@@ -264,11 +564,11 @@ Returns:     nothing
 */
 
 void
-ip_keepalive(int sock, uschar *address, BOOL torf)
+ip_keepalive(int sock, const uschar *address, BOOL torf)
 {
 int fodder = 1;
 if (setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE,
-    (uschar *)(&fodder), sizeof(fodder)) != 0)
+    US (&fodder), sizeof(fodder)) != 0)
   log_write(0, LOG_MAIN, "setsockopt(SO_KEEPALIVE) on connection %s %s "
     "failed: %s", torf? "to":"from", address, strerror(errno));
 }
@@ -279,39 +579,29 @@ if (setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE,
 *         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
+  fd          the file descriptor
+  timelimit   the timeout endpoint, seconds-since-epoch
+Returns:      TRUE => ready for i/o
+              FALSE => timed out, or other error
 */
-
-int
-ip_recv(int sock, uschar *buffer, int buffsize, int timeout)
+BOOL
+fd_ready(int fd, time_t timelimit)
 {
-fd_set select_inset;
-struct timeval tv;
-int start_recv = time(NULL);
-int rc;
+int rc, time_left = timelimit - time(NULL);
 
+if (time_left <= 0)
+  {
+  errno = ETIMEDOUT;
+  return FALSE;
+  }
 /* Wait until the socket is ready */
 
-for (;;)
+do
   {
-  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);
+  /*DEBUG(D_transport) debug_printf("waiting for data on fd\n");*/
+  rc = poll_one_fd(fd, POLLIN, time_left * 1000);
 
   /* 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
@@ -320,40 +610,63 @@ for (;;)
   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. */
+  happening again, we do an explicit time test and adjust the timeout
+  accordingly */
 
   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. */
+    /* Watch out, 'continue' jumps to the condition, not to the loops top */
+    if ((time_left = timelimit - time(NULL)) > 0) continue;
+    }
 
   if (rc <= 0)
     {
     errno = ETIMEDOUT;
-    return -1;
+    return FALSE;
     }
 
-  /* If the socket is ready, break out of the loop. */
-
-  if (FD_ISSET(sock, &select_inset)) break;
+  /* Checking the FD_ISSET is not enough, if we're interrupted, the
+  select_inset may still contain the 'input'. */
   }
+while (rc < 0);
+return TRUE;
+}
+
+/* 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:
+  cctx        the connection context (socket fd, possibly TLS context)
+  buffer      to read into
+  bufsize     the buffer size
+  timelimit   the timeout endpoint, seconds-since-epoch
+
+Returns:      > 0 => that much data read
+              <= 0 on error or EOF; errno set - zero for EOF
+*/
+
+int
+ip_recv(client_conn_ctx * cctx, uschar * buffer, int buffsize, time_t timelimit)
+{
+int rc;
+
+if (!fd_ready(cctx->sock, timelimit))
+  return -1;
 
 /* 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_out.active == sock)
-  rc = tls_read(FALSE, buffer, buffsize);
-else if (tls_in.active == sock)
-  rc = tls_read(TRUE, buffer, buffsize);
+#ifndef DISABLE_TLS
+if (cctx->tls_ctx)					/* client TLS */
+  rc = tls_read(cctx->tls_ctx, buffer, buffsize);
+else if (tls_in.active.sock == cctx->sock)		/* server TLS */
+  rc = tls_read(NULL, buffer, buffsize);
 else
 #endif
-  rc = recv(sock, buffer, buffsize, 0);
+  rc = recv(cctx->sock, buffer, buffsize, 0);
 
 if (rc > 0) return rc;
 if (rc == 0) errno = 0;
@@ -520,13 +833,9 @@ while (last > first)
     return TRUE;
     }
   else if (c > 0)
-    {
     first = middle + 1;
-    }
   else
-    {
     last = middle;
-    }
   }
 return FALSE;
 }
@@ -534,10 +843,11 @@ return FALSE;
 void
 dscp_list_to_stream(FILE *stream)
 {
-int i;
-for (i=0; i < dscp_table_size; ++i)
+for (int i = 0; i < dscp_table_size; ++i)
   fprintf(stream, "%s\n", dscp_table[i].name);
 }
 
 
 /* End of ip.c */
+/* vi: aw ai sw=2
+*/