Add MSG_PEEK support to pflocal

* libpipe/pq.h (packet_peek): Declare new function.
* libpipe/pq.c (packet_read): Move code to new `packet_fetch' function, call it
with `remove' set to 1.
(packet_fetch): New function with code from `packet_read', but do not remove
data if `remove' is 0.
(packet_peek): New function, calls `packet_fetch' with `remove' set to 0.
* libpipe/dgram.c (dgram_read): When MSG_PEEK is in *flags, do not dequeue
and only peek data.
* libpipe/seqpack.c (seqpack_read): Likewise.
* libpipe/stream.c (stream_read): Likewise.
* pflocal/socket.c (S_socket_recv): Pass MSG_PEEK flag to libpipe.

6 files changed, 70 insertions, 14 deletions

diff --git a/libpipe/dgram.c b/libpipe/dgram.c
index 3f3b2ab6..30695f1e 100644
--- a/libpipe/dgram.c
+++ b/libpipe/dgram.c
@@ -40,8 +40,16 @@ static error_t
 dgram_read (struct packet *packet, int *dequeue, unsigned *flags,
 	    char **data, size_t *data_len, size_t amount)
 {
-  *dequeue = 1;
-  return packet_read (packet, data, data_len, amount);
+  if (flags && *flags & MSG_PEEK)
+    {
+      *dequeue = 0;
+      return packet_peek (packet, data, data_len, amount);
+    }
+  else
+    {
+      *dequeue = 1;
+      return packet_read (packet, data, data_len, amount);
+    }
 }
 
 struct pipe_class _dgram_pipe_class =
diff --git a/libpipe/pq.c b/libpipe/pq.c
index afdda051..102f3ee3 100644
--- a/libpipe/pq.c
+++ b/libpipe/pq.c
@@ -349,13 +349,13 @@ packet_write (struct packet *packet,
   return 0;
 }
 
-/* Removes up to AMOUNT bytes from the beginning of the data in PACKET, and
+/* Remove or peek up to AMOUNT bytes from the beginning of the data in PACKET, and
    puts it into *DATA, and the amount read into DATA_LEN.  If more than the
    original *DATA_LEN bytes are available, new memory is vm_allocated, and
    the address and length of this array put into DATA and DATA_LEN.  */
-error_t
-packet_read (struct packet *packet,
-	     char **data, size_t *data_len, size_t amount)
+static error_t
+packet_fetch (struct packet *packet,
+	     char **data, size_t *data_len, size_t amount, int remove)
 {
   char *start = packet->buf_start;
   char *end = packet->buf_end;
@@ -367,7 +367,7 @@ packet_read (struct packet *packet,
     {
       char *buf = packet->buf;
 
-      if (packet->buf_vm_alloced && amount >= vm_page_size)
+      if (remove && packet->buf_vm_alloced && amount >= vm_page_size)
 	/* We can return memory from BUF directly without copying.  */
 	{
 	  if (buf + vm_page_size <= start)
@@ -414,7 +414,7 @@ packet_read (struct packet *packet,
 	  bcopy (start, *data, amount);
 	  start += amount;
 
-	  if (start - buf > 2 * PACKET_SIZE_LARGE)
+	  if (remove && start - buf > 2 * PACKET_SIZE_LARGE)
 	    /* Get rid of unused space at the beginning of the buffer -- we
 	       know it's vm_alloced because of the size, and this will allow
 	       the buffer to just slide through memory.  Because we wait for
@@ -430,10 +430,33 @@ packet_read (struct packet *packet,
 	      packet->buf_len -= dealloc;
 	    }
 
-	  packet->buf_start = start;
+	  if (remove)
+	    packet->buf_start = start;
 	}
     }
   *data_len = amount;
 
   return 0;
 }
+
+/* Removes up to AMOUNT bytes from the beginning of the data in PACKET, and
+   puts it into *DATA, and the amount read into DATA_LEN.  If more than the
+   original *DATA_LEN bytes are available, new memory is vm_allocated, and
+   the address and length of this array put into DATA and DATA_LEN.  */
+error_t
+packet_read (struct packet *packet,
+	     char **data, size_t *data_len, size_t amount)
+{
+  return packet_fetch (packet, data, data_len, amount, 1);
+}
+
+/* Peek up to AMOUNT bytes from the beginning of the data in PACKET, and
+   puts it into *DATA, and the amount read into DATA_LEN.  If more than the
+   original *DATA_LEN bytes are available, new memory is vm_allocated, and
+   the address and length of this array put into DATA and DATA_LEN.  */
+error_t
+packet_peek (struct packet *packet,
+	     char **data, size_t *data_len, size_t amount)
+{
+  return packet_fetch (packet, data, data_len, amount, 0);
+}
diff --git a/libpipe/pq.h b/libpipe/pq.h
index 0fffe254..4e500b6c 100644
--- a/libpipe/pq.h
+++ b/libpipe/pq.h
@@ -98,6 +98,13 @@ error_t packet_write (struct packet *packet,
 error_t packet_read (struct packet *packet,
 		     char **data, size_t *data_len, size_t amount);
 
+/* Peek up to AMOUNT bytes from the beginning of the data in PACKET, and
+   puts it into *DATA, and the amount read into DATA_LEN.  If more than the
+   original *DATA_LEN bytes are available, new memory is vm_allocated, and
+   the address and length of this array put into DATA and DATA_LEN.  */
+error_t packet_peek (struct packet *packet,
+		     char **data, size_t *data_len, size_t amount);
+
 /* Returns any ports in PACKET in PORTS and NUM_PORTS, and removes them from
    PACKET.  */
 error_t packet_read_ports (struct packet *packet,
diff --git a/libpipe/seqpack.c b/libpipe/seqpack.c
index 44a15a03..041abb74 100644
--- a/libpipe/seqpack.c
+++ b/libpipe/seqpack.c
@@ -43,8 +43,17 @@ static error_t
 seqpack_read (struct packet *packet, int *dequeue, unsigned *flags,
 	      char **data, size_t *data_len, size_t amount)
 {
-  error_t err = packet_read (packet, data, data_len, amount);
-  *dequeue = (packet_readable (packet) == 0);
+  error_t err;
+  if (flags && *flags & MSG_PEEK)
+    {
+      err = packet_peek (packet, data, data_len, amount);
+      *dequeue = 0;
+    }
+  else
+    {
+      err = packet_read (packet, data, data_len, amount);
+      *dequeue = (packet_readable (packet) == 0);
+    }
   return err;
 }
 
diff --git a/libpipe/stream.c b/libpipe/stream.c
index 8eb90435..671907e7 100644
--- a/libpipe/stream.c
+++ b/libpipe/stream.c
@@ -56,8 +56,17 @@ static error_t
 stream_read (struct packet *packet, int *dequeue, unsigned *flags,
 	     char **data, size_t *data_len, size_t amount)
 {
-  error_t err = packet_read (packet, data, data_len, amount);
-  *dequeue = (packet_readable (packet) == 0);
+  error_t err;
+  if (flags && *flags & MSG_PEEK)
+    {
+      err = packet_peek (packet, data, data_len, amount);
+      *dequeue = 0;
+    }
+  else
+    {
+      err = packet_read (packet, data, data_len, amount);
+      *dequeue = (packet_readable (packet) == 0);
+    }
   return err;
 }
 
diff --git a/pflocal/socket.c b/pflocal/socket.c
index 2684a723..a0e5b1da 100644
--- a/pflocal/socket.c
+++ b/pflocal/socket.c
@@ -372,7 +372,7 @@ S_socket_recv (struct sock_user *user,
     return EINVAL;		/* XXX */
 
   /* Fill in the pipe FLAGS from any corresponding ones in IN_FLAGS.  */
-  flags = 0;
+  flags = in_flags & MSG_PEEK;
 
   err = sock_acquire_read_pipe (user->sock, &pipe);
   if (err == EPIPE)