[PATCH v3] Add IPv6 support for outgoing remote TCP connections

[Paul Fertser <fercerpav at gmail dot com>]

This patch implements target host lookup the modern way,
see ``man 3 getaddrinfo'' for details; as a result, both IPv4 and IPv6
are transparently supported.

Changes since v1:

* Use gnulib to remain compatible with old systems lacking this
  function.
* Compile-time tested with MinGW-w64 (cross).

Changes since v2:

* Do not use gnulib, handle windows case separately.

gdb:

2014-02-10  Paul Fertser  <fercerpav@gmail.com>

    * ser-tcp.c : Additionally include ws2tcpip.h for windows.
    * ser-tcp.c (net-open): Use last semicolon as port separator.
    * ser-tcp.c (net-open): Use getaddrinfo for host lookup.
    * configure.ac : Add check for getaddrinfo.
    * configure : Regenerated.
---

Interestingly enough, this version continues to try connecting for
about 12 seconds (cycling IPv6 and IPv4 loopback addresess) when run as

./gdb -ex "tar ext :3333"

and nobody's listening.

The same cross-compiled and run with Wine stops trying immediately
(but connects ok if there's a listener). I haven't tried vanilla
version and haven't tried on native windows, so it's hard to tell if
that's a wine artifact.

In this patch I was trying to change current behaviour as little as
possible.

 gdb/configure    |  58 +++++++++++++++++
 gdb/configure.ac |   3 +
 gdb/ser-tcp.c    | 191 +++++++++++++++++++++++++++++--------------------------
 3 files changed, 162 insertions(+), 90 deletions(-)

diff --git a/gdb/configure b/gdb/configure
index 8ae2e09..ea7a9db 100755
--- a/gdb/configure
+++ b/gdb/configure
@@ -6509,6 +6509,64 @@ if test "$ac_res" != no; then :
 fi
 
 
+# Borrow from gnulib, Solaris might additionally need nsl
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for library containing getaddrinfo" >&5
+$as_echo_n "checking for library containing getaddrinfo... " >&6; }
+if test "${ac_cv_search_getaddrinfo+set}" = set; then :
+  $as_echo_n "(cached) " >&6
+else
+  ac_func_search_save_LIBS=$LIBS
+cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+/* Override any GCC internal prototype to avoid an error.
+   Use char because int might match the return type of a GCC
+   builtin and then its argument prototype would still apply.  */
+#ifdef __cplusplus
+extern "C"
+#endif
+char getaddrinfo ();
+int
+main ()
+{
+return getaddrinfo ();
+  ;
+  return 0;
+}
+_ACEOF
+for ac_lib in '' socket network net; do
+  if test -z "$ac_lib"; then
+    ac_res="none required"
+  else
+    ac_res=-l$ac_lib
+    LIBS="-l$ac_lib -lnsl $ac_func_search_save_LIBS"
+  fi
+  if ac_fn_c_try_link "$LINENO"; then :
+  ac_cv_search_getaddrinfo=$ac_res
+fi
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext
+  if test "${ac_cv_search_getaddrinfo+set}" = set; then :
+  break
+fi
+done
+if test "${ac_cv_search_getaddrinfo+set}" = set; then :
+
+else
+  ac_cv_search_getaddrinfo=no
+fi
+rm conftest.$ac_ext
+LIBS=$ac_func_search_save_LIBS
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_search_getaddrinfo" >&5
+$as_echo "$ac_cv_search_getaddrinfo" >&6; }
+ac_res=$ac_cv_search_getaddrinfo
+if test "$ac_res" != no; then :
+  test "$ac_res" = "none required" || LIBS="$ac_res $LIBS"
+
+fi
+
+
 # Some systems (e.g. Solaris) have `socketpair' in libsocket.
 { $as_echo "$as_me:${as_lineno-$LINENO}: checking for library containing socketpair" >&5
 $as_echo_n "checking for library containing socketpair... " >&6; }
diff --git a/gdb/configure.ac b/gdb/configure.ac
index feb28f3..fb14c4b 100644
--- a/gdb/configure.ac
+++ b/gdb/configure.ac
@@ -512,6 +512,9 @@ AC_CHECK_FUNC(wctype, [],
 # Some systems (e.g. Solaris) have `gethostbyname' in libnsl.
 AC_SEARCH_LIBS(gethostbyname, nsl)
 
+# Borrow from gnulib, Solaris might additionally need nsl
+AC_SEARCH_LIBS(getaddrinfo, [socket network net], [], [], [-lnsl])
+
 # Some systems (e.g. Solaris) have `socketpair' in libsocket.
 AC_SEARCH_LIBS(socketpair, socket)
 
diff --git a/gdb/ser-tcp.c b/gdb/ser-tcp.c
index c288ab4..15f7648 100644
--- a/gdb/ser-tcp.c
+++ b/gdb/ser-tcp.c
@@ -39,6 +39,7 @@
 
 #ifdef USE_WIN32API
 #include <winsock2.h>
+#include <ws2tcpip.h>
 #ifndef ETIMEDOUT
 #define ETIMEDOUT WSAETIMEDOUT
 #endif
@@ -157,9 +158,10 @@ int
 net_open (struct serial *scb, const char *name)
 {
   char *port_str, hostname[100];
-  int n, port, tmp;
+  int n, tmp;
   int use_udp;
-  struct hostent *hostent;
+  struct addrinfo hints;
+  struct addrinfo *result, *rp;
   struct sockaddr_in sockaddr;
 #ifdef USE_WIN32API
   u_long ioarg;
@@ -177,7 +179,7 @@ net_open (struct serial *scb, const char *name)
   else if (strncmp (name, "tcp:", 4) == 0)
     name = name + 4;
 
-  port_str = strchr (name, ':');
+  port_str = strrchr (name, ':');
 
   if (!port_str)
     error (_("net_open: No colon in host name!"));  /* Shouldn't ever
@@ -186,124 +188,133 @@ net_open (struct serial *scb, const char *name)
   tmp = min (port_str - name, (int) sizeof hostname - 1);
   strncpy (hostname, name, tmp);	/* Don't want colon.  */
   hostname[tmp] = '\000';	/* Tie off host name.  */
-  port = atoi (port_str + 1);
+  port_str++;
 
   /* Default hostname is localhost.  */
   if (!hostname[0])
     strcpy (hostname, "localhost");
 
-  hostent = gethostbyname (hostname);
-  if (!hostent)
+  memset (&hints, 0, sizeof (struct addrinfo));
+  hints.ai_family = AF_UNSPEC;    /* Allow IPv4 or IPv6 */
+  if (use_udp)
+    hints.ai_socktype = SOCK_DGRAM;
+  else
+    hints.ai_socktype = SOCK_STREAM;
+  hints.ai_flags = 0;
+  hints.ai_protocol = 0;
+
+  tmp = getaddrinfo (hostname, port_str, &hints, &result);
+  if (tmp)
     {
       fprintf_unfiltered (gdb_stderr, "%s: unknown host\n", hostname);
       errno = ENOENT;
       return -1;
     }
 
-  sockaddr.sin_family = PF_INET;
-  sockaddr.sin_port = htons (port);
-  memcpy (&sockaddr.sin_addr.s_addr, hostent->h_addr,
-	  sizeof (struct in_addr));
-
- retry:
-
-  if (use_udp)
-    scb->fd = gdb_socket_cloexec (PF_INET, SOCK_DGRAM, 0);
-  else
-    scb->fd = gdb_socket_cloexec (PF_INET, SOCK_STREAM, 0);
+  for (rp = result; ; rp = rp->ai_next ? rp->ai_next : result)
+    {
+      scb->fd = gdb_socket_cloexec (rp->ai_family, rp->ai_socktype,
+                                    rp->ai_protocol);
 
-  if (scb->fd == -1)
-    return -1;
+      if (scb->fd == -1)
+        continue;
   
-  /* Set socket nonblocking.  */
-  ioarg = 1;
-  ioctl (scb->fd, FIONBIO, &ioarg);
+      /* Set socket nonblocking.  */
+      ioarg = 1;
+      ioctl (scb->fd, FIONBIO, &ioarg);
 
-  /* Use Non-blocking connect.  connect() will return 0 if connected
-     already.  */
-  n = connect (scb->fd, (struct sockaddr *) &sockaddr, sizeof (sockaddr));
+      /* Use Non-blocking connect.  connect() will return 0 if connected
+         already.  */
+      n = connect (scb->fd, rp->ai_addr, rp->ai_addrlen);
 
-  if (n < 0)
-    {
+      if (n < 0)
+        {
 #ifdef USE_WIN32API
-      int err = WSAGetLastError();
+          int err = WSAGetLastError();
 #else
-      int err = errno;
+          int err = errno;
 #endif
 
-      /* Maybe we're waiting for the remote target to become ready to
-	 accept connections.  */
-      if (tcp_auto_retry
+          /* Maybe we're waiting for the remote target to become ready to
+             accept connections.  */
+          if (tcp_auto_retry
 #ifdef USE_WIN32API
-	  && err == WSAECONNREFUSED
+              && err == WSAECONNREFUSED
 #else
-	  && err == ECONNREFUSED
+              && err == ECONNREFUSED
 #endif
-	  && wait_for_connect (NULL, &polls) >= 0)
-	{
-	  close (scb->fd);
-	  goto retry;
-	}
+              && wait_for_connect (NULL, &polls) >= 0)
+            {
+              close (scb->fd);
+              continue;
+            }
 
-      if (
+          if (
 #ifdef USE_WIN32API
-	  /* Under Windows, calling "connect" with a non-blocking socket
-	     results in WSAEWOULDBLOCK, not WSAEINPROGRESS.  */
-	  err != WSAEWOULDBLOCK
+              /* Under Windows, calling "connect" with a non-blocking socket
+                 results in WSAEWOULDBLOCK, not WSAEINPROGRESS.  */
+              err != WSAEWOULDBLOCK
 #else
-	  err != EINPROGRESS
+              err != EINPROGRESS
 #endif
-	  )
-	{
-	  errno = err;
-	  net_close (scb);
-	  return -1;
-	}
-
-      /* Looks like we need to wait for the connect.  */
-      do 
-	{
-	  n = wait_for_connect (scb, &polls);
-	} 
-      while (n == 0);
-      if (n < 0)
-	{
-	  net_close (scb);
-	  return -1;
-	}
-    }
-
-  /* Got something.  Is it an error?  */
-  {
-    int res, err;
-    socklen_t len;
-
-    len = sizeof (err);
-    /* On Windows, the fourth parameter to getsockopt is a "char *";
-       on UNIX systems it is generally "void *".  The cast to "void *"
-       is OK everywhere, since in C "void *" can be implicitly
-       converted to any pointer type.  */
-    res = getsockopt (scb->fd, SOL_SOCKET, SO_ERROR, (void *) &err, &len);
-    if (res < 0 || err)
+              )
+            {
+              errno = err;
+              net_close (scb);
+              freeaddrinfo (result);
+              return -1;
+            }
+
+          /* Looks like we need to wait for the connect.  */
+          do
+            {
+              n = wait_for_connect (scb, &polls);
+            }
+          while (n == 0);
+          if (n < 0)
+            {
+              net_close (scb);
+              freeaddrinfo (result);
+              return -1;
+            }
+        }
+
+      /* Got something.  Is it an error?  */
       {
-	/* Maybe the target still isn't ready to accept the connection.  */
-	if (tcp_auto_retry
+        int res, err;
+        socklen_t len;
+
+        len = sizeof (err);
+        /* On Windows, the fourth parameter to getsockopt is a "char *";
+           on UNIX systems it is generally "void *".  The cast to "void *"
+           is OK everywhere, since in C "void *" can be implicitly
+           converted to any pointer type.  */
+        res = getsockopt (scb->fd, SOL_SOCKET, SO_ERROR, (void *) &err, &len);
+        if (res < 0 || err)
+          {
+            /* Maybe the target still isn't ready to accept the connection.  */
+            if (tcp_auto_retry
 #ifdef USE_WIN32API
-	    && err == WSAECONNREFUSED
+                && err == WSAECONNREFUSED
 #else
-	    && err == ECONNREFUSED
+                && err == ECONNREFUSED
 #endif
-	    && wait_for_connect (NULL, &polls) >= 0)
-	  {
-	    close (scb->fd);
-	    goto retry;
-	  }
-	if (err)
-	  errno = err;
-	net_close (scb);
-	return -1;
+                && wait_for_connect (NULL, &polls) >= 0)
+              {
+                close (scb->fd);
+                continue;
+              }
+            if (err)
+              errno = err;
+            net_close (scb);
+            freeaddrinfo (result);
+            return -1;
+          }
+        break;
       }
-  } 
+    }
+
+  freeaddrinfo (result);
 
   /* Turn off nonblocking.  */
   ioarg = 0;
-- 
1.8.3.2