network: recvmmsg and sendmmsg standard compliance (BZ#16919)

POSIX specifies that both msghdr::msg_iovlen and msghdr::msg_controllen
to be of size int and socklen_t respectively, however Linux implements
it as a size_t.  So for 64-bits architecture where sizeof of size_t is
larger than socklen_t, both sendmmsg and recvmmsg need to adjust the
mmsghdr::msg_hdr internal fields before issuing the syscall itself.

This patch fixes it by operating on the padding if it the case.
For recvmmsg, the most straightfoward case, only zero padding the fields
is suffice.  However, for sendmmsg, where adjusting the buffer is out
of the contract (since it may point to a read-only data), the function
is rewritten to use sendmsg instead (which from previous patch
allocates a temporary msghdr to operate on).

Also for 64-bit ports that requires it, a new recvmmsg and sendmmsg
compat version is created (which uses size_t for both cmsghdr::cmsg_len
and internal

Tested on x86_64, i686, aarch64, armhf, and powerpc64le.

	* sysdeps/unix/sysv/linux/Makefile
	[$(subdir) = socket] (sysdep_routines): Add oldrecvmmsg and
	oldsendmmsg.
	* sysdeps/unix/sysv/linux/aarch64/libc.abilist: Add recvmmsg and
	sendmmsg.
	* sysdeps/unix/sysv/linux/alpha/libc.abilist: Likewise.
	* sysdeps/unix/sysv/linux/ia64/libc.abilist: Likewise.
	* sysdeps/unix/sysv/linux/mips/mips64/n64/libc.abilist: Likewise.
	* sysdeps/sysv/linux/powerpc/powerpc64/libc-le.abilist: Likewise.
	* sysdeps/unix/sysv/linux/powerpc/powerpc64/libc.abilist: Likewise.
	* sysdeps/unix/sysv/linux/s390/s390-64/libc.abilist: Likewise.
	* sysdeps/unix/sysv/linux/sparc/sparc64/libc.abilist: Likewise.
	* sysdeps/unix/sysv/linux/tile/tilegx/tilegx64/libc.abilist:
	Likewise.
	* sysdeps/unix/sysv/linux/x86_64/64/libc.abilist: Likewise.
	* sysdeps/unix/sysv/linux/oldrecvmmsg.c: New file.
	* sysdeps/unix/sysv/linux/oldsendmmsg.c: Likewise.
	* sysdeps/unix/sysv/linux/recvmmsg.c (__recvmmsg): Adjust msghdr
	iovlen and controllen fields to adjust to POSIX specification.
	* sysdeps/unix/sysv/linux/sendmmsg.c (__sendmmsg): Likewise.

sysdeps/unix/sysv/linux/sendmmsg.c

@@ -16,12 +16,10 @@
    License along with the GNU C Library; if not, see
    <http://www.gnu.org/licenses/>.  */
 
-#include <errno.h>
 #include <sys/socket.h>
-
+#include <socketcall.h>
 #include <sysdep-cancel.h>
-#include <sys/syscall.h>
-#include <kernel-features.h>
+#include <shlib-compat.h>
 
 /* Do not use the sendmmsg syscall on socketcall architectures unless
    it was added at the same time as the socketcall support or can be
@@ -32,31 +30,53 @@
 # undef __NR_sendmmsg
 #endif
 
-#ifdef __NR_sendmmsg
-int
-__sendmmsg (int fd, struct mmsghdr *vmessages, unsigned int vlen, int flags)
+#if __WORDSIZE == 64
+static inline int
+send_mmsghdr (int fd, struct mmsghdr *vmessages, unsigned int vlen, int flags)
 {
-  return SYSCALL_CANCEL (sendmmsg, fd, vmessages, vlen, flags);
+  /* Emulate kernel interface for vlen size.  */
+  if (vlen > IOV_MAX)
+    vlen = IOV_MAX;
+  if (vlen == 0)
+    return 0;
+  /* POSIX specifies that both msghdr::msg_iovlen and msghdr::msg_controllen
+     to be int and socklen_t respectively,  however Linux defines it as both
+     size_t.  So for 64-bit it requires some adjustments by copying to
+     temporary header and zeroing the pad fields.
+     The problem is sendmmsg's msghdr may points to an already-filled control
+     buffer and modifying it is not part of sendmmsg contract (the data may
+     be in ro map).  So interact over the msghdr calling the sendmsg that
+     adjust the header using a temporary buffer.  */
+  for (unsigned int i = 0; i < vlen; i++)
+    {
+      ssize_t ret = __sendmsg (fd, &vmessages[i].msg_hdr, flags);
+      if (ret < 0)
+	return -1;
+      vmessages[i].msg_len = ret;
+    }
+  return 1;
 }
-libc_hidden_def (__sendmmsg)
-weak_alias (__sendmmsg, sendmmsg)
-#elif defined __NR_socketcall
-# include <socketcall.h>
-# ifdef __ASSUME_SENDMMSG_SOCKETCALL
-int
-__sendmmsg (int fd, struct mmsghdr *vmessages, unsigned int vlen, int flags)
-{
-  return SOCKETCALL_CANCEL (sendmmsg, fd, vmessages, vlen, flags);
-}
-# else
-static int have_sendmmsg;
+#endif
 
 int
 __sendmmsg (int fd, struct mmsghdr *vmessages, unsigned int vlen, int flags)
 {
+#if __WORDSIZE == 64
+  return send_mmsghdr (fd, vmessages, vlen, flags);
+#elif defined __NR_sendmmsg
+  return SYSCALL_CANCEL (sendmmsg, fd, vmessages, vlen, flags);
+#elif defined __NR_socketcall
+# ifdef __ASSUME_SENDMMSG_SOCKETCALL
+  return SOCKETCALL_CANCEL (sendmmsg, fd, vmessages, vlen, flags);
+# else
+  static int have_sendmmsg;
   if (__glibc_likely (have_sendmmsg >= 0))
     {
+#  if __WORDSIZE == 64
+      int ret = send_mmsghdr (fd, vmessages, vlen, flags);
+#  else
       int ret = SOCKETCALL_CANCEL (sendmmsg, fd, vmessages, vlen, flags);
+#  endif
       /* The kernel returns -EINVAL for unknown socket operations.
 	 We need to convert that error to an ENOSYS error.  */
       if (__builtin_expect (ret < 0, 0)
@@ -84,10 +104,20 @@ __sendmmsg (int fd, struct mmsghdr *vmessages, unsigned int vlen, int flags)
     }
   __set_errno (ENOSYS);
   return -1;
-}
 # endif /* __ASSUME_SENDMMSG_SOCKETCALL  */
-libc_hidden_def (__sendmmsg)
-weak_alias (__sendmmsg, sendmmsg)
-#else
-# include <socket/sendmmsg.c>
+#else /* defined __NR_socketcall  */
+# define STUB 1
+  __set_errno (ENOSYS);
+  return -1;
+#endif
+}
+#ifdef STUB
+stub_warning (sendmmsg)
+#endif
+
+libc_hidden_def (__sendmmsg)
+#if __WORDSIZE == 64
+versioned_symbol (libc, __sendmmsg, sendmmsg, GLIBC_2_24);
+#else
+weak_alias (__sendmmsg, sendmmsg)
 #endif