[syslog-ng] user-bound UDP socket

[Bryan Henderson]

Here's a patch that adds an option to the UDP source to specify the
file descriptor of an already bound UDP socket, in lieu of having
syslog-ng create and bind the socket.

This makes it possible to run syslog-ng without the privilege required
to bind to reserved UDP port numbers (such as the standard syslog port
number).  I exec syslog-ng with no privileges at all, except write
permission to the log files.

Aside from the config file processing, all the patch does is skip the
call to afsocket_open_socket() if the user supplied a file descriptor,
and move the settings of the nonblock and close-on-exec options from
afsocket_open_socket() to afsocket_setup_socket().

-- 
Bryan Henderson                                   San Jose, California


diff --rec --unif syslog-ng-2.0.2+20070202/src/afinet.c syslog-ng/src/afinet.c
--- syslog-ng-2.0.2+20070202/src/afinet.c	2007-02-01 23:11:48.000000000 +0000
+++ syslog-ng/src/afinet.c	2007-02-02 17:26:26.000000000 +0000
@@ -233,6 +233,15 @@
   afinet_resolve_name(self->bind_addr, ip);
 }
 
+void 
+afinet_sd_set_fd(LogDriver *s, int fd)
+{
+  AFSocketSourceDriver *self = (AFSocketSourceDriver *) s;
+  
+  self->user_fd = fd;
+  self->user_bound_socket = TRUE;
+}
+
 static gboolean
 afinet_sd_setup_socket(AFSocketSourceDriver *s, gint fd)
 {
diff --rec --unif syslog-ng-2.0.2+20070202/src/afinet.h syslog-ng/src/afinet.h
--- syslog-ng-2.0.2+20070202/src/afinet.h	2007-02-01 23:11:40.000000000 +0000
+++ syslog-ng/src/afinet.h	2007-02-02 17:26:26.000000000 +0000
@@ -42,6 +42,7 @@
 LogDriver *afinet_sd_new(gint af, gchar *host, gint port, guint flags);
 void afinet_sd_set_localport(LogDriver *self, gint port, gchar *service, gchar *proto);
 void afinet_sd_set_localip(LogDriver *self, gchar *ip);
+void afinet_sd_set_fd(LogDriver *s, int fd);
 
 #define afinet_sd_set_auth(a,b)
 #define afinet_sd_set_mac(a,b)
--- syslog-ng-2.0.2+20070202/src/afsocket.c	2007-02-01 23:11:47.000000000 +0000
+++ syslog-ng/src/afsocket.c	2007-02-09 03:00:27.000000000 +0000
@@ -157,6 +157,9 @@
 gboolean
 afsocket_setup_socket(gint fd, SocketOptions *sock_options, AFSocketDirection dir)
 {
+  g_fd_set_nonblock(fd, TRUE);
+  g_fd_set_cloexec(sock, TRUE);
+
   if (dir & AFSOCKET_DIR_RECV)
     {
       if (sock_options->rcvbuf)
@@ -183,8 +186,6 @@
   else
     sock = socket(bind_addr->sa.sa_family, SOCK_DGRAM, 0);
     
-  g_fd_set_nonblock(sock, TRUE);
-  g_fd_set_cloexec(sock, TRUE);
   if (sock != -1)
     {
       if (g_bind(sock, bind_addr) != G_IO_STATUS_NORMAL)
@@ -390,9 +391,6 @@
       return TRUE;
     }
     
-  g_fd_set_nonblock(new_fd, TRUE);
-  g_fd_set_cloexec(new_fd, TRUE);
-    
   msg_verbose("Syslog connection accepted",
               evt_tag_str("from", g_sockaddr_format(peer_addr, buf1, sizeof(buf1))),
               evt_tag_str("to", g_sockaddr_format(self->bind_addr, buf2, sizeof(buf2))),
@@ -492,8 +490,13 @@
     {
       if (!self->connections)
         {
-          if (!afsocket_open_socket(self->bind_addr, !!(self->flags & AFSOCKET_STREAM), &sock))
-            return self->super.optional;
+          if (self->user_bound_socket)
+            sock = self->user_fd;
+          else {
+            if (!afsocket_open_socket(self->bind_addr, !!(self->flags & AFSOCKET_STREAM), &sock))
+              return self->super.optional;
+          }
+
         }
       self->fd = -1;
 
@@ -633,6 +636,7 @@
   self->max_connections = 10;
   self->listen_backlog = 255;
   self->flags = flags;
+  self->user_bound_socket = FALSE;
   log_reader_options_defaults(&self->reader_options);
 }
 
diff --rec --unif syslog-ng-2.0.2+20070202/src/afsocket.h syslog-ng/src/afsocket.h
--- syslog-ng-2.0.2+20070202/src/afsocket.h	2007-02-01 23:11:47.000000000 +0000
+++ syslog-ng/src/afsocket.h	2007-02-02 17:26:26.000000000 +0000
@@ -61,6 +61,8 @@
   guint source_id;
   LogReaderOptions reader_options;
 
+  gboolean user_bound_socket;
+  int user_fd;
   GSockAddr *bind_addr;
   gint max_connections;
   gint num_connections;
diff --rec --unif syslog-ng-2.0.2+20070202/src/cfg-grammar.y syslog-ng/src/cfg-grammar.y
--- syslog-ng-2.0.2+20070202/src/cfg-grammar.y	2007-02-01 23:11:47.000000000 +0000
+++ syslog-ng/src/cfg-grammar.y	2007-02-02 17:26:26.000000000 +0000
@@ -94,7 +94,7 @@
 
 /* socket related options */
 %token KW_KEEP_ALIVE KW_MAX_CONNECTIONS
-%token KW_LOCALIP KW_IP KW_LOCALPORT KW_PORT KW_DESTPORT 
+%token KW_LOCALIP KW_IP KW_LOCALPORT KW_PORT KW_DESTPORT KW_FD
 %token KW_IP_TTL KW_SO_BROADCAST KW_IP_TOS KW_SO_SNDBUF KW_SO_RCVBUF KW_SO_KEEPALIVE
 
 /* misc options */
@@ -371,6 +371,7 @@
 	: source_afinet_option
 	| KW_LOCALPORT '(' string ')'		{ afinet_sd_set_localport(last_driver, 0, $3, "udp"); free($3); }
 	| KW_PORT '(' string ')'		{ afinet_sd_set_localport(last_driver, 0, $3, "udp"); free($3); }
+	| KW_FD '(' NUMBER ')'		{ afinet_sd_set_fd(last_driver, $3); }
 	;
 
 source_afinet_option
@@ -904,4 +905,4 @@
   last_reader_options = NULL;
   last_writer_options = NULL;
   last_template = NULL;
-}
\ No newline at end of file
+}
diff --rec --unif syslog-ng-2.0.2+20070202/src/cfg-lex.l syslog-ng/src/cfg-lex.l
--- syslog-ng-2.0.2+20070202/src/cfg-lex.l	2007-02-01 23:11:47.000000000 +0000
+++ syslog-ng/src/cfg-lex.l	2007-02-02 17:26:26.000000000 +0000
@@ -119,6 +119,7 @@
 	{ "localport",		KW_LOCALPORT },
 	{ "port",		KW_PORT },
 	{ "destport",		KW_DESTPORT },
+	{ "fd",		        KW_FD },
         { "ip_ttl",             KW_IP_TTL },
         { "ip_tos",             KW_IP_TOS },
         { "so_broadcast",       KW_SO_BROADCAST },