Re: [tschwinge/sendmmsg] Add recvmmsg and sendmmsg to the generic glibc API

[Thomas Schwinge <thomas at codesourcery dot com>]

Hi!

On Fri,  2 Nov 2012 12:38:00 -0700 (PDT), Roland McGrath <roland@hack.frob.com> wrote:
> [...]

Thanks for the explanation of name spaces and related symbol internals.
I now have a better understanding of this.


Here is the latest version of the patch.  I have also recreated the
tschwinge/sendmmsg branch (90a40232b8bd4973002718aacfcfd793139a7ff5).
Primarily I have addressed Roland's comments: move __sendmmsg to
GLIBC_PRIVATE, and restore recvmmsg to not have an internal __recvmmsg
symbol.

For testing, I have also done additional builds on x86 and x86-64
GNU/Linux with the following patch applied:

diff --git sysdeps/unix/sysv/linux/internal_sendmmsg.S sysdeps/unix/sysv/linux/internal_sendmmsg.S
index e6681f0..bb71cc6 100644
--- sysdeps/unix/sysv/linux/internal_sendmmsg.S
+++ sysdeps/unix/sysv/linux/internal_sendmmsg.S
@@ -1,5 +1,8 @@
 #include <kernel-features.h>
 #include <sys/syscall.h>
+
+#undef __NR_sendmmsg
+
 #if !defined __NR_sendmmsg && defined __NR_socketcall
 # define socket	sendmmsg
 # ifndef __ASSUME_SENDMMSG
diff --git sysdeps/unix/sysv/linux/sendmmsg.c sysdeps/unix/sysv/linux/sendmmsg.c
index a6daff1..3310d78 100644
--- sysdeps/unix/sysv/linux/sendmmsg.c
+++ sysdeps/unix/sysv/linux/sendmmsg.c
@@ -23,6 +23,7 @@
 #include <sys/syscall.h>
 #include <kernel-features.h>
 
+#undef __NR_sendmmsg
 
 #ifdef __NR_sendmmsg
 int

This exercises the case that there is no sendmmsg syscall.  On x86, the
socketcall interface will instead be used.  On x86-64, there is no
socketcall interface, so the ENOSYS stub will be used.  All
socket/{internal_,}sendmmsg.o{,s} files look as I'd expecte them to look.

2012-11-01  Thomas Schwinge  <thomas@codesourcery.com>

	* sysdeps/unix/sysv/linux/bits/socket.h (struct mmsghdr, recvmmsg)
	(sendmmsg): Move declarations...
	* socket/sys/socket.h: ... here.
	* sysdeps/unix/sysv/linux/recvmmsg.c [!defined __NR_recvmmsg &&
	!defined __NR_socketcall] (recvmmsg): Move ENOSYS stub into and
	include it from...
	* socket/recvmmsg.c: ... this new file.
	* sysdeps/unix/sysv/linux/internal_sendmmsg.S [__ASSUME_SENDMMSG]
	(sendmmsg): Rename to __sendmmsg, create weak alias and make
	definition of __sendmmsg hidden.
	* sysdeps/unix/sysv/linux/sendmmsg.c (sendmmsg): Likewise.
	[!defined __NR_sendmmsg && !defined __NR_socketcall] (sendmmsg):
	Move ENOSYS stub into and include it from...
	* socket/sendmmsg.c: ... this new file.
	* sysdeps/unix/sysv/linux/Makefile [subdir=socket]
	(sysdep_routines): Move recvmmsg and sendmmsg...
	* socket/Makefile (routines): ... here.
	* socket/Versions (GLIBC_2.17): Add recvmmsg and sendmmsg.
	(GLIBC_PRIVATE): Add __sendmmsg.
	* include/sys/socket.h (__sendmmsg): Add declarations.
	* resolv/res_send.c (send_dg): Invoke __sendmmsg instead of
	sendmmsg.


diff --git include/sys/socket.h include/sys/socket.h
index ec08857..9caf1bb 100644
--- include/sys/socket.h
+++ include/sys/socket.h
@@ -91,6 +91,10 @@ extern ssize_t __libc_sendmsg (int __fd, const struct msghdr *__message,
 extern ssize_t __sendmsg (int __fd, const struct msghdr *__message,
 			  int __flags) attribute_hidden;
 
+extern int __sendmmsg (int __fd, struct mmsghdr *__vmessages,
+                       unsigned int __vlen, int __flags);
+libc_hidden_proto (__sendmmsg)
+
 /* Receive a message as described by MESSAGE from socket FD.
    Returns the number of bytes read or -1 for errors.  */
 extern ssize_t __libc_recvmsg (int __fd, struct msghdr *__message,
diff --git resolv/res_send.c resolv/res_send.c
index 0a28cd7..c790031 100644
--- resolv/res_send.c
+++ resolv/res_send.c
@@ -1129,7 +1129,7 @@ send_dg(res_state statp,
 		    reqs[1].msg_hdr.msg_control = NULL;
 		    reqs[1].msg_hdr.msg_controllen = 0;
 
-		    int ndg = sendmmsg (pfd[0].fd, reqs, 2, MSG_NOSIGNAL);
+		    int ndg = __sendmmsg (pfd[0].fd, reqs, 2, MSG_NOSIGNAL);
 		    if (__builtin_expect (ndg == 2, 1))
 		      {
 			if (reqs[0].msg_len != buflen
diff --git socket/Makefile socket/Makefile
index e3a90b8..6037f3f 100644
--- socket/Makefile
+++ socket/Makefile
@@ -26,7 +26,7 @@ headers	:= sys/socket.h sys/un.h bits/sockaddr.h bits/socket.h \
 routines := accept bind connect getpeername getsockname getsockopt	\
 	    listen recv recvfrom recvmsg send sendmsg sendto		\
 	    setsockopt shutdown socket socketpair isfdtype opensock	\
-	    sockatmark accept4
+	    sockatmark accept4 recvmmsg sendmmsg
 
 aux	 := have_sock_cloexec
 
diff --git socket/Versions socket/Versions
index 7a96b1e..dcad329 100644
--- socket/Versions
+++ socket/Versions
@@ -34,4 +34,10 @@ libc {
   GLIBC_2.10 {
     accept4;
   }
+  GLIBC_2.17 {
+    recvmmsg; sendmmsg;
+  }
+  GLIBC_PRIVATE {
+    __sendmmsg;
+  }
 }
diff --git socket/recvmmsg.c socket/recvmmsg.c
new file mode 100644
index 0000000..2d6d474
--- /dev/null
+++ socket/recvmmsg.c
@@ -0,0 +1,31 @@
+/* Receive multiple messages on a socket.  Stub version.
+   Copyright (C) 2010-2012 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <errno.h>
+#include <sys/socket.h>
+
+/* Receive up to VLEN messages as described by VMESSAGES from socket FD.
+   Returns the number of bytes read or -1 for errors.  */
+int
+recvmmsg (int fd, struct mmsghdr *vmessages, unsigned int vlen, int flags,
+	  const struct timespec *tmo)
+{
+  __set_errno (ENOSYS);
+  return -1;
+}
+stub_warning (recvmmsg)
diff --git socket/sendmmsg.c socket/sendmmsg.c
new file mode 100644
index 0000000..ed93f49
--- /dev/null
+++ socket/sendmmsg.c
@@ -0,0 +1,32 @@
+/* Send multiple messages on a socket.  Stub version.
+   Copyright (C) 2011-2012 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <errno.h>
+#include <sys/socket.h>
+
+/* Send a VLEN messages as described by VMESSAGES to socket FD.
+   Returns the number of datagrams successfully written or -1 for errors.  */
+int
+__sendmmsg (int fd, struct mmsghdr *vmessages, unsigned int vlen, int flags)
+{
+  __set_errno (ENOSYS);
+  return -1;
+}
+libc_hidden_def (__sendmmsg)
+weak_alias (__sendmmsg, sendmmsg)
+stub_warning (sendmmsg)
diff --git socket/sys/socket.h socket/sys/socket.h
index 787c2b9..3810a37 100644
--- socket/sys/socket.h
+++ socket/sys/socket.h
@@ -97,6 +97,16 @@ typedef union { __SOCKADDR_ALLTYPES
 # undef __SOCKADDR_ONETYPE
 #endif
 
+#ifdef __USE_GNU
+/* For `recvmmsg' and `sendmmsg'.  */
+struct mmsghdr
+  {
+    struct msghdr msg_hdr;	/* Actual message header.  */
+    unsigned int msg_len;	/* Number of received or sent bytes for the
+				   entry.  */
+  };
+#endif
+
 
 /* Create a new socket of type TYPE in domain DOMAIN, using
    protocol PROTOCOL.  If PROTOCOL is zero, one is chosen automatically.
@@ -175,6 +185,16 @@ extern ssize_t recvfrom (int __fd, void *__restrict __buf, size_t __n,
 extern ssize_t sendmsg (int __fd, const struct msghdr *__message,
 			int __flags);
 
+#ifdef __USE_GNU
+/* Send a VLEN messages as described by VMESSAGES to socket FD.
+   Returns the number of datagrams successfully written or -1 for errors.
+
+   This function is a cancellation point and therefore not marked with
+   __THROW.  */
+extern int sendmmsg (int __fd, struct mmsghdr *__vmessages,
+		     unsigned int __vlen, int __flags);
+#endif
+
 /* Receive a message as described by MESSAGE from socket FD.
    Returns the number of bytes read or -1 for errors.
 
@@ -182,6 +202,17 @@ extern ssize_t sendmsg (int __fd, const struct msghdr *__message,
    __THROW.  */
 extern ssize_t recvmsg (int __fd, struct msghdr *__message, int __flags);
 
+#ifdef __USE_GNU
+/* Receive up to VLEN messages as described by VMESSAGES from socket FD.
+   Returns the number of bytes read or -1 for errors.
+
+   This function is a cancellation point and therefore not marked with
+   __THROW.  */
+extern int recvmmsg (int __fd, struct mmsghdr *__vmessages,
+		     unsigned int __vlen, int __flags,
+		     const struct timespec *__tmo);
+#endif
+
 
 /* Put the current value for socket FD's option OPTNAME at protocol level LEVEL
    into OPTVAL (which is *OPTLEN bytes long), and set *OPTLEN to the value's
diff --git sysdeps/unix/sysv/linux/Makefile sysdeps/unix/sysv/linux/Makefile
index 8e5361c..ecd9c2c 100644
--- sysdeps/unix/sysv/linux/Makefile
+++ sysdeps/unix/sysv/linux/Makefile
@@ -12,8 +12,7 @@ CFLAGS-malloc.c += -DMORECORE_CLEARS=2
 endif
 
 ifeq ($(subdir),socket)
-sysdep_routines += internal_accept4 recvmmsg internal_recvmmsg sendmmsg \
-		   internal_sendmmsg
+sysdep_routines += internal_accept4 internal_recvmmsg internal_sendmmsg
 endif
 
 ifeq ($(subdir),misc)
diff --git sysdeps/unix/sysv/linux/bits/socket.h sysdeps/unix/sysv/linux/bits/socket.h
index 309cba7..df8f167 100644
--- sysdeps/unix/sysv/linux/bits/socket.h
+++ sysdeps/unix/sysv/linux/bits/socket.h
@@ -235,16 +235,6 @@ struct msghdr
     int msg_flags;		/* Flags on received message.  */
   };
 
-#ifdef __USE_GNU
-/* For `recvmmsg' and 'sendmmsg'.  */
-struct mmsghdr
-  {
-    struct msghdr msg_hdr;	/* Actual message header.  */
-    unsigned int msg_len;	/* Number of received or sent bytes
-				   for the entry.  */
-  };
-#endif
-
 /* Structure used for storage of ancillary data object information.  */
 struct cmsghdr
   {
@@ -389,27 +379,4 @@ struct linger
     int l_linger;		/* Time to linger.  */
   };
 
-
-__BEGIN_DECLS
-
-#ifdef __USE_GNU
-/* Receive up to VLEN messages as described by VMESSAGES from socket FD.
-   Returns the number of bytes read or -1 for errors.
-
-   This function is a cancellation point and therefore not marked with
-   __THROW.  */
-extern int recvmmsg (int __fd, struct mmsghdr *__vmessages,
-		     unsigned int __vlen, int __flags,
-		     const struct timespec *__tmo);
-
-/* Send a VLEN messages as described by VMESSAGES to socket FD.
-   Return the number of datagrams successfully written or -1 for errors.
-This function is a cancellation point and therefore not marked with
-   __THROW.  */
-extern int sendmmsg (int __fd, struct mmsghdr *__vmessages,
-		     unsigned int __vlen, int __flags);
-#endif
-
-__END_DECLS
-
 #endif	/* bits/socket.h */
diff --git sysdeps/unix/sysv/linux/internal_sendmmsg.S sysdeps/unix/sysv/linux/internal_sendmmsg.S
index f5152c9..e6681f0 100644
--- sysdeps/unix/sysv/linux/internal_sendmmsg.S
+++ sysdeps/unix/sysv/linux/internal_sendmmsg.S
@@ -2,13 +2,14 @@
 #include <sys/syscall.h>
 #if !defined __NR_sendmmsg && defined __NR_socketcall
 # define socket	sendmmsg
-# ifdef __ASSUME_SENDMMSG
-#  define __socket sendmmsg
-# else
+# ifndef __ASSUME_SENDMMSG
 #  define __socket __internal_sendmmsg
+#  define NO_WEAK_ALIAS
 # endif
 # define NARGS 4
 # define NEED_CANCELLATION
-# define NO_WEAK_ALIAS
 # include <socket.S>
+# ifdef __ASSUME_SENDMMSG
+libc_hidden_def (__sendmmsg)
+# endif
 #endif
diff --git sysdeps/unix/sysv/linux/recvmmsg.c sysdeps/unix/sysv/linux/recvmmsg.c
index 32fc8df..009d868 100644
--- sysdeps/unix/sysv/linux/recvmmsg.c
+++ sysdeps/unix/sysv/linux/recvmmsg.c
@@ -1,4 +1,4 @@
-/* Copyright (C) 2010 Free Software Foundation, Inc.
+/* Copyright (C) 2010-2012 Free Software Foundation, Inc.
    This file is part of the GNU C Library.
    Contributed by Andreas Schwab <schwab@redhat.com>, 2010.
 
@@ -88,12 +88,5 @@ recvmmsg (int fd, struct mmsghdr *vmessages, unsigned int vlen, int flags,
 /* When __ASSUME_RECVMMSG recvmmsg is defined in internal_recvmmsg.S.  */
 # endif
 #else
-int
-recvmmsg (int fd, struct mmsghdr *vmessages, unsigned int vlen, int flags,
-	  const struct timespec *tmo)
-{
-  __set_errno (ENOSYS);
-  return -1;
-}
-stub_warning (recvmmsg)
+# include <socket/recvmmsg.c>
 #endif
diff --git sysdeps/unix/sysv/linux/sendmmsg.c sysdeps/unix/sysv/linux/sendmmsg.c
index 0674419..a6daff1 100644
--- sysdeps/unix/sysv/linux/sendmmsg.c
+++ sysdeps/unix/sysv/linux/sendmmsg.c
@@ -1,4 +1,4 @@
-/* Copyright (C) 2011 Free Software Foundation, Inc.
+/* Copyright (C) 2011-2012 Free Software Foundation, Inc.
    This file is part of the GNU C Library.
    Contributed by Ulrich Drepper <drepper@gmail.com>, 2011.
 
@@ -26,7 +26,7 @@
 
 #ifdef __NR_sendmmsg
 int
-sendmmsg (int fd, struct mmsghdr *vmessages, unsigned int vlen, int flags)
+__sendmmsg (int fd, struct mmsghdr *vmessages, unsigned int vlen, int flags)
 {
   if (SINGLE_THREAD_P)
     return INLINE_SYSCALL (sendmmsg, 4, fd, vmessages, vlen, flags);
@@ -39,6 +39,8 @@ sendmmsg (int fd, struct mmsghdr *vmessages, unsigned int vlen, int flags)
 
   return result;
 }
+libc_hidden_def (__sendmmsg)
+weak_alias (__sendmmsg, sendmmsg)
 #elif defined __NR_socketcall
 # ifndef __ASSUME_SENDMMSG
 extern int __internal_sendmmsg (int fd, struct mmsghdr *vmessages,
@@ -48,7 +50,7 @@ extern int __internal_sendmmsg (int fd, struct mmsghdr *vmessages,
 static int have_sendmmsg;
 
 int
-sendmmsg (int fd, struct mmsghdr *vmessages, unsigned int vlen, int flags)
+__sendmmsg (int fd, struct mmsghdr *vmessages, unsigned int vlen, int flags)
 {
   if (__builtin_expect (have_sendmmsg >= 0, 1))
     {
@@ -81,15 +83,11 @@ sendmmsg (int fd, struct mmsghdr *vmessages, unsigned int vlen, int flags)
   __set_errno (ENOSYS);
   return -1;
 }
+libc_hidden_def (__sendmmsg)
+weak_alias (__sendmmsg, sendmmsg)
 # else
 /* When __ASSUME_SENDMMSG sendmmsg is defined in internal_sendmmsg.S.  */
 # endif
 #else
-int
-sendmmsg (int fd, struct mmsghdr *vmessages, unsigned int vlen, int flags)
-{
-  __set_errno (ENOSYS);
-  return -1;
-}
-stub_warning (sendmmsg)
+# include <socket/sendmmsg.c>
 #endif


GrÃÃe,
 Thomas

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