Add ares_set_socket_configure_callback()

This function sets a callback that is invoked after the socket is
created, but before the connection is established.  This is an ideal
time to customize various socket options.

Makefile.inc

@@ -116,6 +116,7 @@ MANPAGES = ares_cancel.3		\
   ares_set_servers_ports.3		\
   ares_set_servers_ports_csv.3		\
   ares_set_socket_callback.3		\
+  ares_set_socket_configure_callback.3	\
   ares_set_sortlist.3			\
   ares_strerror.3			\
   ares_timeout.3			\
@@ -167,6 +168,7 @@ HTMLPAGES = ares_cancel.html		\
   ares_set_servers_ports.html			\
   ares_set_servers_ports_csv.html			\
   ares_set_socket_callback.html		\
+  ares_set_socket_configure_callback.html		\
   ares_set_sortlist.html			\
   ares_strerror.html			\
   ares_timeout.html			\
@@ -218,6 +220,7 @@ PDFPAGES = ares_cancel.pdf		\
   ares_set_servers_ports.pdf			\
   ares_set_servers_ports_csv.pdf			\
   ares_set_socket_callback.pdf		\
+  ares_set_socket_configure_callback.pdf		\
   ares_set_sortlist.pdf			\
   ares_strerror.pdf			\
   ares_timeout.pdf			\

ares.h

@@ -294,6 +294,10 @@ typedef int  (*ares_sock_create_callback)(ares_socket_t socket_fd,
                                           int type,
                                           void *data);
 
+typedef int  (*ares_sock_config_callback)(ares_socket_t socket_fd,
+                                          int type,
+                                          void *data);
+
 CARES_EXTERN int ares_library_init(int flags);
 
 CARES_EXTERN int ares_library_init_mem(int flags,
@@ -344,6 +348,10 @@ CARES_EXTERN void ares_set_socket_callback(ares_channel channel,
                                            ares_sock_create_callback callback,
                                            void *user_data);
 
+CARES_EXTERN void ares_set_socket_configure_callback(ares_channel channel,
+                                                     ares_sock_config_callback callback,
+                                                     void *user_data);
+
 CARES_EXTERN int ares_set_sortlist(ares_channel channel,
                                    const char *sortstr);
 

ares_init.c

@@ -164,6 +164,8 @@ int ares_init_options(ares_channel *channelptr, struct ares_options *options,
   channel->sock_state_cb_data = NULL;
   channel->sock_create_cb = NULL;
   channel->sock_create_cb_data = NULL;
+  channel->sock_config_cb = NULL;
+  channel->sock_config_cb_data = NULL;
 
   channel->last_server = 0;
   channel->last_timeout_processed = (time_t)now.tv_sec;
@@ -291,6 +293,8 @@ int ares_dup(ares_channel *dest, ares_channel src)
   /* Now clone the options that ares_save_options() doesn't support. */
   (*dest)->sock_create_cb      = src->sock_create_cb;
   (*dest)->sock_create_cb_data = src->sock_create_cb_data;
+  (*dest)->sock_config_cb      = src->sock_config_cb;
+  (*dest)->sock_config_cb_data = src->sock_config_cb_data;
 
   strncpy((*dest)->local_dev_name, src->local_dev_name,
           sizeof(src->local_dev_name));
@@ -2085,6 +2089,14 @@ void ares_set_socket_callback(ares_channel channel,
   channel->sock_create_cb_data = data;
 }
 
+void ares_set_socket_configure_callback(ares_channel channel,
+                                        ares_sock_config_callback cb,
+                                        void *data)
+{
+  channel->sock_config_cb = cb;
+  channel->sock_config_cb_data = data;
+}
+
 int ares_set_sortlist(ares_channel channel, const char *sortstr)
 {
   int nsort = 0;

ares_private.h

@@ -311,6 +311,9 @@ struct ares_channeldata {
 
   ares_sock_create_callback sock_create_cb;
   void *sock_create_cb_data;
+
+  ares_sock_config_callback sock_config_cb;
+  void *sock_config_cb_data;
 };
 
 /* Memory management functions */

ares_process.c

@@ -1031,6 +1031,17 @@ static int open_tcp_socket(ares_channel channel, struct server_state *server)
     }
 #endif
 
+  if (channel->sock_config_cb)
+    {
+      int err = channel->sock_config_cb(s, SOCK_STREAM,
+                                        channel->sock_config_cb_data);
+      if (err < 0)
+        {
+          sclose(s);
+          return err;
+        }
+    }
+
   /* Connect to the server. */
   if (connect(s, sa, salen) == -1)
     {
@@ -1115,6 +1126,17 @@ static int open_udp_socket(ares_channel channel, struct server_state *server)
        return -1;
     }
 
+  if (channel->sock_config_cb)
+    {
+      int err = channel->sock_config_cb(s, SOCK_DGRAM,
+                                        channel->sock_config_cb_data);
+      if (err < 0)
+        {
+          sclose(s);
+          return err;
+        }
+    }
+
   /* Connect to the server. */
   if (connect(s, sa, salen) == -1)
     {

ares_set_socket_callback.3

@@ -20,7 +20,7 @@ connected to the remote server. The callback must return ARES_SUCCESS if
 things are fine, or use the standard ares error codes to signal errors
 back. Returned errors will abort the ares operation.
 .SH SEE ALSO
-.BR ares_init_options (3)
+.BR ares_init_options (3), ares_set_socket_configure_callback (3)
 .SH AVAILABILITY
 ares_set_socket_callback(3) was added in c-ares 1.6.0
 .SH AUTHOR

ares_set_socket_configure_callback.3

@@ -0,0 +1,33 @@
+.\"
+.TH ARES_SET_SOCKET_CONFIGURE_CALLBACK 3 "6 Feb 2016"
+.SH NAME
+ares_set_socket_configure_callback \- Set a socket configuration callback
+.SH SYNOPSIS
+.nf
+.B #include <ares.h>
+.PP
+.B typedef int (*ares_sock_config_callback)(ares_socket_t \fIsocket_fd\fP,
+                                         int \fItype\fP,
+                                         void *\fIuserdata\fP)
+.PP
+.B void ares_set_socket_configure_callback(ares_channel \fIchannel\fP,
+                             ares_sock_config_callback \fIcallback\fP,
+                             void *\fIuserdata\fP)
+.PP
+.B cc file.c -lcares
+.fi
+.SH DESCRIPTION
+.PP
+This function sets a \fIcallback\fP in the given ares channel handle. This
+callback function will be invoked after the socket has been created, but
+before it has been connected to the remote server, which is an ideal time
+to configure various socket options.  The callback must return ARES_SUCCESS
+if things are fine, or return -1 to signal an error. A returned error will
+abort the ares operation.
+.SH SEE ALSO
+.BR ares_init_options (3), ares_set_socket_callback (3)
+.SH AVAILABILITY
+ares_set_socket_configure_callback(3) was added in c-ares 1.11.0
+.SH AUTHOR
+Andrew Ayer
+

test/ares-test-mock.cc

@@ -153,6 +153,51 @@ TEST_P(MockChannelTest, SockFailCallback) {
   EXPECT_EQ(ARES_ECONNREFUSED, result.status_);
 }
 
+static int sock_config_cb_count = 0;
+static int SocketConfigureCallback(ares_socket_t fd, int type, void *data) {
+  int rc = *(int*)data;
+  if (verbose) std::cerr << "SocketConfigureCallback(" << fd << ") invoked" << std::endl;
+  sock_config_cb_count++;
+  return rc;
+}
+
+TEST_P(MockChannelTest, SockConfigureCallback) {
+  DNSPacket rsp;
+  rsp.set_response().set_aa()
+    .add_question(new DNSQuestion("www.google.com", ns_t_a))
+    .add_answer(new DNSARR("www.google.com", 100, {2, 3, 4, 5}));
+  EXPECT_CALL(server_, OnRequest("www.google.com", ns_t_a))
+    .WillOnce(SetReply(&server_, &rsp));
+
+  // Get notified of new sockets
+  int rc = ARES_SUCCESS;
+  ares_set_socket_configure_callback(channel_, SocketConfigureCallback, &rc);
+
+  HostResult result;
+  sock_config_cb_count = 0;
+  ares_gethostbyname(channel_, "www.google.com.", AF_INET, HostCallback, &result);
+  Process();
+  EXPECT_EQ(1, sock_config_cb_count);
+  EXPECT_TRUE(result.done_);
+  std::stringstream ss;
+  ss << result.host_;
+  EXPECT_EQ("{'www.google.com' aliases=[] addrs=[2.3.4.5]}", ss.str());
+}
+
+TEST_P(MockChannelTest, SockConfigureFailCallback) {
+  // Notification of new sockets gives an error.
+  int rc = -1;
+  ares_set_socket_configure_callback(channel_, SocketConfigureCallback, &rc);
+
+  HostResult result;
+  sock_config_cb_count = 0;
+  ares_gethostbyname(channel_, "www.google.com.", AF_INET, HostCallback, &result);
+  Process();
+  EXPECT_LT(1, sock_config_cb_count);
+  EXPECT_TRUE(result.done_);
+  EXPECT_EQ(ARES_ECONNREFUSED, result.status_);
+}
+
 // TCP only to prevent retries
 TEST_P(MockTCPChannelTest, MalformedResponse) {
   std::vector<byte> one = {0x01};