commit 4d480f55ae79cd3b3d1b2681a852e8317a23c977
Author: Marco Nenciarini <mnencia@debian.org>
Date:   Tue Jul 11 16:08:40 2006 -0700

    http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=376914
    
    some libsysfs2 internal stucts are corrupted during execution of brctl
    by unneeded and erroneous calls to sysfs_close_class_device()
    
    Long description of my troubles
    
    On my xen Dom0 with 5 bridges and many interfaces every brctl show
    invocations fails with a strange error.
    
    bridge name     bridge id               STP enabled     interfaces
    xenbr0          8000.feffffffffff       no              vif1.0
                                                            peth0
                                                            vif0.0
    xenbr1          8000.feffffffffff       no              vif3.0
                                                            vif2.0
                                                            vif1.1
                                                            peth1
                                                            vif0.1
    xenbr2          8000.feffffffffff       no              vif1.2
                                                            peth2
                                                            vif0.2
    xenbr3          8000.feffffffffff       no               can't get port info: No such device
    xenbr4          8000.feffffffffff       no              vif2.2
                                                            peth4
                                                            vif0.4
    
    but xenbr3 was fully up and functional, as stated by the contents of
    /sys/class/net/xenbr3 directory.
    
    Investigating with strace i've found that brctl give this error
    because it is trying to read xenbr3 interfaces in
    /sys/class/net/eth0/brif directory!
    
    .....
    lstat64("/sys/class/net/xenbr3/bridge/topology_change_detected", {st_mode=S_IFREG|0444, st_size=4096, ...}) = 0
    stat64("/sys/class/net/xenbr3/bridge/topology_change_detected", {st_mode=S_IFREG|0444, st_size=4096, ...}) = 0
    open("/sys/class/net/xenbr3/bridge/topology_change_detected", O_RDONLY) = 4
    read(4, "0\n", 4096)                    = 2
    close(4)                                = 0
    open("/sys/class/net/eth0/brif", O_RDONLY|O_NONBLOCK|O_LARGEFILE|O_DIRECTORY) = -1 ENOENT (No such file or directory)
    ioctl(3, SIOCDEVPRIVATE, 0xafdec36c)    = -1 ENODEV (No such device)
    write(1, "8000.feffffffffff\tno\t\t can\'t get"..., 59) = 59
    lstat64("/sys/class/net/xenbr4/bridge", {st_mode=S_IFDIR|0755, st_size=0, ...}) = 0
    write(1, "xenbr4\t\t", 8)               = 8
    .....
    
    after some gdb and documentation reading sessions i've discovered that
    all calls to sysfs_close_class_device() in libbridge code are wrong,
    because their arguments are pointers returned by sysfs_get_*
    functions. This is explicitly forbidden by libsysfs documentation[1]
    at 6.1.b and corrupt libsysfs internal structures freeing memory that
    still being used.
    
    [1] /usr/share/doc/libsysfs-dev/libsysfs.txt.gz
    
    .....
    6.1 Calling Conventions in Libsysfs
    -----------------------------------
    
    Libsysfs uses a simple API calling convention. APIs are classified to be
    one of "open", "get", "close" types. The convention is as follows:
    
            a. All "open" APIs have a corresponding "close" API.
            b. References obtained using "get" calls should not be closed
                    explicitly.
            c. All "opened" references have to be closed with a call to
                    their corresponding "close" call. This takes care of
                    freeing structure references obtained with "get" calls.
    .....
    
    I have checked all other sysfs_close_* calls and they seem to be
    correct.
    
    Attached patch removes the wrong call, so i can operate correctly on
    my bridges.

diff --git a/libbridge/libbridge_devif.c b/libbridge/libbridge_devif.c
index d3052a1..3703f4b 100644
--- a/libbridge/libbridge_devif.c
+++ b/libbridge/libbridge_devif.c
@@ -188,7 +188,6 @@ #ifdef HAVE_LIBSYSFS
 	snprintf(path, SYSFS_PATH_MAX, "%s/bridge", dev->path);
 	if (sysfs_path_is_dir(path)) {
 		dprintf("path '%s' is not a directory\n", path);
-		sysfs_close_class_device(dev);
 		goto fallback;
 	}
 
@@ -214,7 +213,6 @@ #ifdef HAVE_LIBSYSFS
 	info->topology_change = fetch_int(dev, BRIDGEATTR("topology_change"));
 	info->topology_change_detected = fetch_int(dev, 
 						   BRIDGEATTR("topology_change_detected"));
-	sysfs_close_class_device(dev);
 
 	return 0;
 
@@ -287,7 +285,6 @@ #ifdef HAVE_LIBSYSFS
 
 	snprintf(path, SYSFS_PATH_MAX, "%s/brport", dev->path);
 	if (sysfs_path_is_dir(path)) {
-		sysfs_close_class_device(dev);
 		goto fallback;
 	}
 
@@ -309,7 +306,6 @@ #ifdef HAVE_LIBSYSFS
 		 &info->forward_delay_timer_value);
 	fetch_tv(dev, BRPORT("hold_timer"),
 		 &info->hold_timer_value);
-	sysfs_close_class_device(dev);
 
 	return 0;
 fallback:
@@ -339,7 +335,6 @@ #ifdef HAVE_LIBSYSFS
 			ret = sysfs_write_attribute(attr, buf, strlen(buf));
 			sysfs_close_attribute(attr);
 		}
-		sysfs_close_class_device(dev);
 	} else
 #endif
 	{
@@ -411,7 +406,6 @@ #ifdef HAVE_LIBSYSFS
 			ret = sysfs_write_attribute(attr, buf, strlen(buf));
 			sysfs_close_attribute(attr);
 		}
-		sysfs_close_class_device(dev);
 	} else
 #endif
 	{