Linux: Only generate 64 bit timestamps for 64 bit time_t recvmsg/recvmmsg

The timestamps created by __convert_scm_timestamps only make sense for
64 bit time_t programs, 32 bit time_t programs will ignore 64 bit time_t
timestamps since SO_TIMESTAMP will be defined to old values (either by
glibc or kernel headers).

Worse, if the buffer is not suffice MSG_CTRUNC is set to indicate it
(which breaks some programs [1]).

This patch makes only 64 bit time_t recvmsg and recvmmsg to call
__convert_scm_timestamps.  Also, the assumption to called it is changed
from __ASSUME_TIME64_SYSCALLS to __TIMESIZE != 64 since the setsockopt
might be called by libraries built without __TIME_BITS=64.  The
MSG_CTRUNC is only set for the 64 bit symbols, it should happen only
if 64 bit time_t programs run older kernels.

Checked on x86_64-linux-gnu and i686-linux-gnu.

[1] https://github.com/systemd/systemd/pull/20567

Reviewed-by: Florian Weimer <fweimer@redhat.com>

include/sys/socket.h

@@ -98,15 +98,21 @@ extern int __sendmmsg (int __fd, struct mmsghdr *__vmessages,
 libc_hidden_proto (__sendmmsg)
 #endif
 
-/* 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,
 			       int __flags);
 extern ssize_t __recvmsg (int __fd, struct msghdr *__message,
 			  int __flags) attribute_hidden;
 #if __TIMESIZE == 64
+# define __libc_recvmsg64 __libc_recvmsg
+# define __recvmsg64  __recvmsg
 # define __recvmmsg64 __recvmmsg
 #else
+extern ssize_t __libc_recvmsg64 (int __fd, struct msghdr *__message,
+				 int __flags);
+extern ssize_t __recvmsg64 (int __fd, struct msghdr *__message,
+			    int __flags);
+/* Receive a message as described by MESSAGE from socket FD.
+   Returns the number of bytes read or -1 for errors.  */
 extern int __recvmmsg64 (int __fd, struct mmsghdr *vmessages,
 			 unsigned int vlen, int flags,
 			 struct __timespec64 *timeout);

sysdeps/unix/sysv/linux/Makefile

@@ -277,8 +277,14 @@ sysdep_routines += cmsg_nxthdr
 CFLAGS-recvmmsg.c = -fexceptions -fasynchronous-unwind-tables
 CFLAGS-sendmmsg.c = -fexceptions -fasynchronous-unwind-tables
 
-tests += tst-socket-timestamp
-tests-time64 += tst-socket-timestamp-time64
+tests += \
+  tst-socket-timestamp \
+  tst-socket-timestamp-compat \
+  # tests
+tests-time64 += \
+  tst-socket-timestamp-time64 \
+  tst-socket-timestamp-compat-time64
+  # tests-time64
 
 tests-special += $(objpfx)tst-socket-consts.out
 $(objpfx)tst-socket-consts.out: ../sysdeps/unix/sysv/linux/tst-socket-consts.py

sysdeps/unix/sysv/linux/recvmmsg.c

@@ -19,9 +19,9 @@
 #include <sysdep.h>
 #include <socketcall.h>
 
-int
-__recvmmsg64 (int fd, struct mmsghdr *vmessages, unsigned int vlen, int flags,
-	      struct __timespec64 *timeout)
+static int
+recvmmsg_syscall (int fd, struct mmsghdr *vmessages, unsigned int vlen,
+		  int flags, struct __timespec64 *timeout)
 {
 #ifndef __NR_recvmmsg_time64
 # define __NR_recvmmsg_time64 __NR_recvmmsg
@@ -44,12 +44,6 @@ __recvmmsg64 (int fd, struct mmsghdr *vmessages, unsigned int vlen, int flags,
       pts32 = &ts32;
     }
 
-  socklen_t csize[IOV_MAX];
-  if (vlen > IOV_MAX)
-    vlen = IOV_MAX;
-  for (int i = 0; i < vlen; i++)
-    csize[i] = vmessages[i].msg_hdr.msg_controllen;
-
 # ifdef __ASSUME_RECVMMSG_SYSCALL
   r = SYSCALL_CANCEL (recvmmsg, fd, vmessages, vlen, flags, pts32);
 # else
@@ -59,11 +53,31 @@ __recvmmsg64 (int fd, struct mmsghdr *vmessages, unsigned int vlen, int flags,
     {
       if (timeout != NULL)
         *timeout = valid_timespec_to_timespec64 (ts32);
+    }
+#endif
+  return r;
+}
 
+int
+__recvmmsg64 (int fd, struct mmsghdr *vmessages, unsigned int vlen, int flags,
+	      struct __timespec64 *timeout)
+{
+#if __TIMESIZE != 64
+  socklen_t csize[IOV_MAX];
+  if (vlen > IOV_MAX)
+    vlen = IOV_MAX;
+  for (int i = 0; i < vlen; i++)
+    csize[i] = vmessages[i].msg_hdr.msg_controllen;
+#endif
+
+  int r = recvmmsg_syscall (fd, vmessages, vlen, flags, timeout);
+#if __TIMESIZE != 64
+  if (r > 0)
+    {
       for (int i=0; i < r; i++)
         __convert_scm_timestamps (&vmessages[i].msg_hdr, csize[i]);
     }
-#endif /* __ASSUME_TIME64_SYSCALLS  */
+#endif
   return r;
 }
 #if __TIMESIZE != 64
@@ -79,7 +93,7 @@ __recvmmsg (int fd, struct mmsghdr *vmessages, unsigned int vlen, int flags,
       ts64 = valid_timespec_to_timespec64 (*timeout);
       pts64 = &ts64;
     }
-  int r = __recvmmsg64 (fd, vmessages, vlen, flags, pts64);
+  int r = recvmmsg_syscall (fd, vmessages, vlen, flags, pts64);
   if (r >= 0 && timeout != NULL)
     /* The remanining timeout will be always less the input TIMEOUT.  */
     *timeout = valid_timespec64_to_timespec (ts64);

sysdeps/unix/sysv/linux/recvmsg.c

@@ -20,29 +20,41 @@
 #include <sysdep-cancel.h>
 #include <socketcall.h>
 
+static int
+__recvmsg_syscall (int fd, struct msghdr *msg, int flags)
+{
+#ifdef __ASSUME_RECVMSG_SYSCALL
+  return SYSCALL_CANCEL (recvmsg, fd, msg, flags);
+#else
+  return SOCKETCALL_CANCEL (recvmsg, fd, msg, flags);
+#endif
+}
+
 ssize_t
-__libc_recvmsg (int fd, struct msghdr *msg, int flags)
+__libc_recvmsg64 (int fd, struct msghdr *msg, int flags)
 {
   ssize_t r;
-#ifndef __ASSUME_TIME64_SYSCALLS
+#if __TIMESIZE != 64
   socklen_t orig_controllen = msg != NULL ? msg->msg_controllen : 0;
 #endif
 
-#ifdef __ASSUME_RECVMSG_SYSCALL
-  r = SYSCALL_CANCEL (recvmsg, fd, msg, flags);
-#else
-  r = SOCKETCALL_CANCEL (recvmsg, fd, msg, flags);
-#endif
+  r = __recvmsg_syscall (fd, msg, flags);
 
-#ifndef __ASSUME_TIME64_SYSCALLS
+#if __TIMESIZE != 64
   if (r >= 0 && orig_controllen != 0)
     __convert_scm_timestamps (msg, orig_controllen);
 #endif
 
   return r;
 }
+#if __TIMESIZE != 64
+weak_alias (__libc_recvmsg64, __recvmsg64)
+
+ssize_t
+__libc_recvmsg (int fd, struct msghdr *msg, int flags)
+{
+  return __recvmsg_syscall (fd, msg, flags);
+}
+#endif
 weak_alias (__libc_recvmsg, recvmsg)
 weak_alias (__libc_recvmsg, __recvmsg)
-#if __TIMESIZE != 64
-weak_alias (__recvmsg, __recvmsg64)
-#endif

sysdeps/unix/sysv/linux/tst-socket-timestamp-compat-time64.c

@@ -0,0 +1 @@
+#include "tst-socket-timestamp-compat.c"

sysdeps/unix/sysv/linux/tst-socket-timestamp-compat.c

@@ -0,0 +1,265 @@
+/* Check recvmsg/recvmmsg 64-bit timestamp support.
+   Copyright (C) 2022 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
+   <https://www.gnu.org/licenses/>.  */
+
+#include <arpa/inet.h>
+#include <string.h>
+#include <support/check.h>
+#include <support/xsocket.h>
+#include <support/xunistd.h>
+#include <stdbool.h>
+
+/* AF_INET socket and address used to receive data.  */
+static int srv;
+static struct sockaddr_in srv_addr;
+
+static int
+do_sendto (const struct sockaddr_in *addr, int payload)
+{
+  int s = xsocket (AF_INET, SOCK_DGRAM | SOCK_CLOEXEC, 0);
+  xconnect (s, (const struct sockaddr *) addr, sizeof (*addr));
+
+  xsendto (s, &payload, sizeof (payload), 0, (const struct sockaddr *) addr,
+	   sizeof (*addr));
+
+  xclose (s);
+
+  return 0;
+}
+
+static void
+do_recvmsg_ancillary (bool use_multi_call, struct mmsghdr *mmhdr,
+		      void *msgbuf, size_t msgbuflen, int exp_payload)
+{
+  int payload;
+  struct iovec iov =
+    {
+      .iov_base = &payload,
+      .iov_len = sizeof (payload)
+    };
+  mmhdr->msg_hdr.msg_name = NULL;
+  mmhdr->msg_hdr.msg_iov = &iov;
+  mmhdr->msg_hdr.msg_iovlen = 1;
+  mmhdr->msg_hdr.msg_control = msgbuf;
+  mmhdr->msg_hdr.msg_controllen = msgbuflen;
+
+  int r;
+  if (use_multi_call)
+    {
+      r = recvmmsg (srv, mmhdr, 1, 0, NULL);
+      if (r >= 0)
+	r = mmhdr->msg_len;
+    }
+  else
+    r = recvmsg (srv, &mmhdr->msg_hdr, 0);
+  TEST_COMPARE (r, sizeof (int));
+  TEST_COMPARE (payload, exp_payload);
+}
+
+/* Check if recvmsg create the additional 64 bit timestamp if only 32 bit
+   is enabled for 64 bit recvmsg symbol.  */
+static void
+do_test_large_buffer (bool mc)
+{
+  struct mmsghdr mmhdr = { 0 };
+  /* It should be large enought for either timeval/timespec and the
+     64 time type as well.  */
+
+  union
+  {
+    struct cmsghdr cmsghdr;
+    char msgbuf[512];
+  } control;
+
+  /* Enable 32 bit timeval precision and check if no 64 bit timeval stamp
+     is created.  */
+  {
+    int r = setsockopt (srv, SOL_SOCKET, SO_TIMESTAMP_OLD, &(int){1},
+			sizeof (int));
+    TEST_VERIFY_EXIT (r != -1);
+
+    do_sendto (&srv_addr, 42);
+    do_recvmsg_ancillary (mc, &mmhdr, &control, sizeof control, 42);
+
+    bool found_timestamp = false;
+    for (struct cmsghdr *cmsg = CMSG_FIRSTHDR (&mmhdr.msg_hdr);
+	 cmsg != NULL;
+	 cmsg = CMSG_NXTHDR (&mmhdr.msg_hdr, cmsg))
+    {
+      if (cmsg->cmsg_level != SOL_SOCKET)
+	continue;
+
+      if (sizeof (time_t) > 4 && cmsg->cmsg_type == SO_TIMESTAMP_NEW)
+	found_timestamp = true;
+      else
+	TEST_VERIFY (cmsg->cmsg_type != SO_TIMESTAMP_NEW);
+    }
+
+    TEST_COMPARE (found_timestamp, sizeof (time_t) > 4);
+  }
+
+  /* Same as before, but for timespec.  */
+  {
+    int r = setsockopt (srv, SOL_SOCKET, SO_TIMESTAMPNS_OLD, &(int){1},
+			sizeof (int));
+    TEST_VERIFY_EXIT (r != -1);
+
+    do_sendto (&srv_addr, 42);
+    do_recvmsg_ancillary (mc, &mmhdr, &control, sizeof control, 42);
+
+    bool found_timestamp = false;
+    for (struct cmsghdr *cmsg = CMSG_FIRSTHDR (&mmhdr.msg_hdr);
+	 cmsg != NULL;
+	 cmsg = CMSG_NXTHDR (&mmhdr.msg_hdr, cmsg))
+    {
+      if (cmsg->cmsg_level != SOL_SOCKET)
+	continue;
+
+      if (sizeof (time_t) > 4 && cmsg->cmsg_type == SO_TIMESTAMPNS_NEW)
+	found_timestamp = true;
+      else
+	TEST_VERIFY (cmsg->cmsg_type != SO_TIMESTAMPNS_NEW);
+    }
+
+    TEST_COMPARE (found_timestamp, sizeof (time_t) > 4);
+  }
+}
+
+/* Check if recvmsg does not create the additional 64 bit timestamp if
+   only 32 bit timestamp is enabled if the ancillary buffer is not large
+   enought.  Also checks if MSG_CTRUNC is set iff for 64 bit recvmsg
+   symbol.  */
+static void
+do_test_small_buffer (bool mc)
+{
+  struct mmsghdr mmhdr = { 0 };
+
+  /* Enable 32 bit timeval precision and check if no 64 bit timeval stamp
+     is created.  */
+  {
+    int r = setsockopt (srv, SOL_SOCKET, SO_TIMESTAMP_OLD, &(int){1},
+			sizeof (int));
+    TEST_VERIFY_EXIT (r != -1);
+
+    union
+    {
+      struct cmsghdr cmsghdr;
+      char msgbuf[CMSG_SPACE (sizeof (struct timeval))];
+    } control;
+
+    do_sendto (&srv_addr, 42);
+    do_recvmsg_ancillary (mc, &mmhdr, &control, sizeof control, 42);
+
+    bool found_timestamp = false;
+    for (struct cmsghdr *cmsg = CMSG_FIRSTHDR (&mmhdr.msg_hdr);
+	 cmsg != NULL;
+	 cmsg = CMSG_NXTHDR (&mmhdr.msg_hdr, cmsg))
+    {
+      if (cmsg->cmsg_level != SOL_SOCKET)
+	continue;
+
+      if (sizeof (time_t) > 4 && cmsg->cmsg_type == SO_TIMESTAMP_NEW)
+	found_timestamp = true;
+      else
+	TEST_VERIFY (cmsg->cmsg_type != SO_TIMESTAMP_NEW);
+    }
+
+    if (sizeof (time_t) > 4)
+      {
+	TEST_VERIFY ((mmhdr.msg_hdr.msg_flags & MSG_CTRUNC));
+	TEST_COMPARE (found_timestamp, 0);
+      }
+    else
+      {
+	TEST_VERIFY (!(mmhdr.msg_hdr.msg_flags & MSG_CTRUNC));
+	TEST_COMPARE (found_timestamp, 0);
+      }
+  }
+
+  /* Same as before, but for timespec.  */
+  {
+    int r = setsockopt (srv, SOL_SOCKET, SO_TIMESTAMPNS_OLD, &(int){1},
+			sizeof (int));
+    TEST_VERIFY_EXIT (r != -1);
+
+    union
+    {
+      struct cmsghdr cmsghdr;
+      char msgbuf[CMSG_SPACE (sizeof (struct timespec))];
+    } control;
+
+    do_sendto (&srv_addr, 42);
+    do_recvmsg_ancillary (mc, &mmhdr, &control, sizeof control, 42);
+
+    bool found_timestamp = false;
+    for (struct cmsghdr *cmsg = CMSG_FIRSTHDR (&mmhdr.msg_hdr);
+	 cmsg != NULL;
+	 cmsg = CMSG_NXTHDR (&mmhdr.msg_hdr, cmsg))
+    {
+      if (cmsg->cmsg_level != SOL_SOCKET)
+	continue;
+
+      if (sizeof (time_t) > 4 && cmsg->cmsg_type == SO_TIMESTAMPNS_NEW)
+	found_timestamp = true;
+      else
+	TEST_VERIFY (cmsg->cmsg_type != SO_TIMESTAMPNS_NEW);
+    }
+
+    if (sizeof (time_t) > 4)
+      {
+	TEST_VERIFY ((mmhdr.msg_hdr.msg_flags & MSG_CTRUNC));
+	TEST_COMPARE (found_timestamp, 0);
+      }
+    else
+      {
+	TEST_VERIFY ((mmhdr.msg_hdr.msg_flags & MSG_CTRUNC) == 0);
+	TEST_COMPARE (found_timestamp, 0);
+      }
+  }
+}
+
+static int
+do_test (void)
+{
+  /* This test only make sense for ABIs that support 32 bit time_t socket
+     timestampss.  */
+  if (sizeof (time_t) > 4 && __WORDSIZE == 64)
+    return 0;
+
+  srv = xsocket (AF_INET, SOCK_DGRAM, 0);
+  srv_addr = (struct sockaddr_in) {
+    .sin_family = AF_INET,
+    .sin_addr = {.s_addr = htonl (INADDR_LOOPBACK) },
+  };
+  xbind (srv, (struct sockaddr *) &srv_addr, sizeof (srv_addr));
+  {
+    socklen_t sa_len = sizeof (srv_addr);
+    xgetsockname (srv, (struct sockaddr *) &srv_addr, &sa_len);
+    TEST_VERIFY (sa_len == sizeof (srv_addr));
+  }
+
+  /* Check recvmsg;  */
+  do_test_large_buffer (false);
+  do_test_small_buffer (false);
+  /* Check recvmmsg.  */
+  do_test_large_buffer (true);
+  do_test_small_buffer (true);
+
+  return 0;
+}
+
+#include <support/test-driver.c>