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Date:      Fri, 31 Jul 2015 20:02:13 +0000 (UTC)
From:      Luiz Otavio O Souza <loos@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org
Subject:   svn commit: r286139 - head/sys/net
Message-ID:  <201507312002.t6VK2Dc3002634@repo.freebsd.org>
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Author: loos
Date: Fri Jul 31 20:02:12 2015
New Revision: 286139
URL: https://svnweb.freebsd.org/changeset/base/286139

Log:
  Do not allocate the buffers at opening of the descriptor, because once
  the buffer is allocated we are committed to a particular buffer method
  (BPF_BUFMODE_BUFFER in this case).
  
  If we are using zero-copy buffers, the userland program must register its
  buffers before set the interface.
  
  If we are using kernel memory buffers, we can allocate the buffer at the
  time that the interface is being set.
  
  This fix allows the usage of BIOCSETBUFMODE after r235746.
  
  Update the comments to reflect the recent changes.
  
  MFC after:	2 weeks
  Sponsored by:	Rubicon Communications (Netgate)

Modified:
  head/sys/net/bpf.c

Modified: head/sys/net/bpf.c
==============================================================================
--- head/sys/net/bpf.c	Fri Jul 31 17:41:53 2015	(r286138)
+++ head/sys/net/bpf.c	Fri Jul 31 20:02:12 2015	(r286139)
@@ -862,7 +862,7 @@ static	int
 bpfopen(struct cdev *dev, int flags, int fmt, struct thread *td)
 {
 	struct bpf_d *d;
-	int error, size;
+	int error;
 
 	d = malloc(sizeof(*d), M_BPF, M_WAITOK | M_ZERO);
 	error = devfs_set_cdevpriv(d, bpf_dtor);
@@ -892,10 +892,6 @@ bpfopen(struct cdev *dev, int flags, int
 	callout_init_mtx(&d->bd_callout, &d->bd_lock, 0);
 	knlist_init_mtx(&d->bd_sel.si_note, &d->bd_lock);
 
-	/* Allocate default buffers */
-	size = d->bd_bufsize;
-	bpf_buffer_ioctl_sblen(d, &size);
-
 	return (0);
 }
 
@@ -1472,10 +1468,33 @@ bpfioctl(struct cdev *dev, u_long cmd, c
 	 * Set interface.
 	 */
 	case BIOCSETIF:
-		BPF_LOCK();
-		error = bpf_setif(d, (struct ifreq *)addr);
-		BPF_UNLOCK();
-		break;
+		{
+			int alloc_buf, size;
+
+			/*
+			 * Behavior here depends on the buffering model.  If
+			 * we're using kernel memory buffers, then we can
+			 * allocate them here.  If we're using zero-copy,
+			 * then the user process must have registered buffers
+			 * by the time we get here.
+			 */
+			alloc_buf = 0;
+			BPFD_LOCK(d);
+			if (d->bd_bufmode == BPF_BUFMODE_BUFFER &&
+			    d->bd_sbuf == NULL)
+				alloc_buf = 1;
+			BPFD_UNLOCK(d);
+			if (alloc_buf) {
+				size = d->bd_bufsize;
+				error = bpf_buffer_ioctl_sblen(d, &size);
+				if (error != 0)
+					break;
+			}
+			BPF_LOCK();
+			error = bpf_setif(d, (struct ifreq *)addr);
+			BPF_UNLOCK();
+			break;
+		}
 
 	/*
 	 * Set read timeout.
@@ -1912,10 +1931,8 @@ bpf_setif(struct bpf_d *d, struct ifreq 
 	BPFIF_RUNLOCK(bp);
 
 	/*
-	 * Behavior here depends on the buffering model.  If we're using
-	 * kernel memory buffers, then we can allocate them here.  If we're
-	 * using zero-copy, then the user process must have registered
-	 * buffers by the time we get here.  If not, return an error.
+	 * At this point, we expect the buffer is already allocated.  If not,
+	 * return an error.
 	 */
 	switch (d->bd_bufmode) {
 	case BPF_BUFMODE_BUFFER:

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