Allow s6-ipcserver-socketbinder to create SOCK_DGRAM sockets and to not listen() (suggested by Daniel Kahn Gillmor)

2 files changed, 23 insertions, 9 deletions

diff --git a/doc/s6-ipcserver-socketbinder.html b/doc/s6-ipcserver-socketbinder.html
index 8f9d990..9bfaec5 100644
--- a/doc/s6-ipcserver-socketbinder.html
+++ b/doc/s6-ipcserver-socketbinder.html
@@ -26,11 +26,11 @@ socket, then executes a program.
 <h2> Interface </h2>
 
 <pre>
-     s6-ipcserver-socketbinder [ -d | -D ] [ -b <em>backlog</em> ] <em>path</em> <em>prog...</em>
+     s6-ipcserver-socketbinder [ -d | -D ] [ -b <em>backlog</em> ] [ -M | -m ] <em>path</em> <em>prog...</em>
 </pre>
 
 <ul>
- <li> s6-ipcserver-socketbinder creates a Unix domain socket of type SOCK_STREAM
+ <li> s6-ipcserver-socketbinder creates a Unix domain socket
 and binds it to <em>path</em>. It prepares the socket to accept
 connections by calling
 <a href="http://pubs.opengroup.org/onlinepubs/9699919799/functions/listen.html">listen()</a>. </li>
@@ -48,8 +48,17 @@ and is generally used with server programs. This is the default. Note that
 <em>path</em> will be deleted if it already exists at program start time. </li>
  <li> <tt>-D</tt>&nbsp;: disallow instant rebinding to the same path. </li>
  <li> <tt>-b&nbsp;<em>backlog</em></tt>&nbsp;: set a maximum of
-<em>backlog</em> backlog connections on the socket. Extra
-connection attempts will rejected by the kernel. </li>
+<em>backlog</em> backlog connections on the socket - extra
+connection attempts will rejected by the kernel. The default is SOMAXCONN,
+i.e. the maximum number allowed by the system. If <em>backlog</em>
+is 0, then the socket will be created, but it <strong>will not be
+listening</em>. </li>
+ <li> <tt>-M</tt>&nbsp;: the type of the socket will be SOCK_STREAM. This is
+the default. </li>
+ <li> <tt>-m</tt>&nbsp;: the type of the socket will be SOCK_DGRAM. Note
+that by default SOCK_DGRAM sockets are not connection-mode, and <tt>listen()</tt>
+will fail - so you should always give the <tt>-b0</tt> option to
+s6-ipcserver-socketbinder along with <tt>-m</tt>. </li>
 </ul>
 
 <h2> Notes </h2>
diff --git a/src/conn-tools/s6-ipcserver-socketbinder.c b/src/conn-tools/s6-ipcserver-socketbinder.c
index b5a32f3..523b118 100644
--- a/src/conn-tools/s6-ipcserver-socketbinder.c
+++ b/src/conn-tools/s6-ipcserver-socketbinder.c
@@ -2,6 +2,7 @@
 
 #include <sys/types.h>
 #include <sys/stat.h>
+#include <sys/socket.h>
 #include <unistd.h>
 #include <skalibs/uint.h>
 #include <skalibs/sgetopt.h>
@@ -9,24 +10,27 @@
 #include <skalibs/djbunix.h>
 #include <skalibs/webipc.h>
 
-#define USAGE "s6-ipcserver-socketbinder [ -d | -D ] [ -b backlog ] path prog..."
+#define USAGE "s6-ipcserver-socketbinder [ -d | -D ] [ -b backlog ] [ -M | -m ] path prog..."
 #define dieusage() strerr_dieusage(100, USAGE)
 
 int main (int argc, char const *const *argv, char const *const *envp)
 {
-  unsigned int backlog = 20 ;
+  unsigned int backlog = SOMAXCONN ;
   int flagreuse = 1 ;
+  int flagdgram = 0 ;
   PROG = "s6-ipcserver-socketbinder" ;
   {
     subgetopt_t l = SUBGETOPT_ZERO ;
     for (;;)
     {
-      register int opt = subgetopt_r(argc, argv, "Ddb:", &l) ;
+      register int opt = subgetopt_r(argc, argv, "DdMmb:", &l) ;
       if (opt == -1) break ;
       switch (opt)
       {
         case 'D' : flagreuse = 0 ; break ;
         case 'd' : flagreuse = 1 ; break ;
+        case 'M' : flagdgram = 0 ; break ;
+        case 'm' : flagdgram = 1 ; break ;
         case 'b' : if (!uint0_scan(l.arg, &backlog)) dieusage() ; break ;
         default : dieusage() ;
       }
@@ -35,14 +39,15 @@ int main (int argc, char const *const *argv, char const *const *envp)
   }
   if (argc < 2) dieusage() ;
   close(0) ;
-  if (ipc_stream()) strerr_diefu1sys(111, "create socket") ;
+  if (flagdgram ? ipc_datagram() : ipc_stream()) strerr_diefu1sys(111, "create socket") ;
   {
     mode_t m = umask(0) ;
     if ((flagreuse ? ipc_bind_reuse(0, argv[0]) : ipc_bind(0, argv[0])) < 0)
       strerr_diefu2sys(111, "bind to ", argv[0]) ;
     umask(m) ;
   }
-  if (ipc_listen(0, backlog) < 0) strerr_diefu2sys(111, "listen to ", argv[0]) ;
+  if (backlog && ipc_listen(0, backlog) < 0)
+    strerr_diefu2sys(111, "listen to ", argv[0]) ;
 
   pathexec_run(argv[1], argv + 1, envp) ;
   strerr_dieexec(111, argv[1]) ;