Changes from Pavel Kankovsky to reset the kernel filter in

"pcap_setfilter()" if we're not using a kernel filter, in case a
previous call to "pcap_setfilter()" had succeeded in adding a kernel
filter, as if we're doing userland filtering we need to get rid of all
kernel filters that might discard packets that'd pass the userland
filter.

diff --git a/pcap-linux.c b/pcap-linux.c
index e3cad64680dfb8bb3c0154084482705caaabe031..67f32fab2c057a1b59455aeee712c7f59310b80c 100644 (file)
--- a/pcap-linux.c
+++ b/pcap-linux.c
@@ -26,7 +26,7 @@
  */
 #ifndef lint
 static const char rcsid[] =
-    "@(#) $Header: /tcpdump/master/libpcap/pcap-linux.c,v 1.65 2001-08-25 05:08:26 guy Exp $ (LBL)";
+    "@(#) $Header: /tcpdump/master/libpcap/pcap-linux.c,v 1.66 2001-08-30 03:08:43 guy Exp $ (LBL)";
 #endif
 
 /*
@@ -190,6 +190,7 @@ static int  iface_bind_old(int fd, const char *device, char *ebuf);
 static int     fix_program(pcap_t *handle, struct sock_fprog *fcode);
 static int     fix_offset(struct bpf_insn *p);
 static int     set_kernel_filter(pcap_t *handle, struct sock_fprog *fcode);
+static int     reset_kernel_filter(pcap_t *handle);
 
 static struct sock_filter      total_insn
        = BPF_STMT(BPF_RET | BPF_K, 0);
@@ -759,6 +760,17 @@ pcap_setfilter(pcap_t *handle, struct bpf_program *filter)
                }
        }
 
+       /*
+        * If we're not using the kernel filter, get rid of any kernel
+        * filter that might've been there before, e.g. because the
+        * previous filter could work in the kernel, or because some other
+        * code attached a filter to the socket by some means other than
+        * calling "pcap_setfilter()".  Otherwise, the kernel filter may
+        * filter out packets that would pass the new userland filter.
+        */
+       if (!handle->md.use_bpf)
+               reset_kernel_filter(handle);
+
        /*
         * Free up the copy of the filter that was made by "fix_program()".
         */
@@ -1555,8 +1567,6 @@ set_kernel_filter(pcap_t *handle, struct sock_fprog *fcode)
        int save_mode;
        int ret;
        int save_errno;
-       /* setsockopt() barfs unless it get a dummy parameter */
-       int dummy;
 
        /*
         * The socket filter code doesn't discard all packets queued
@@ -1594,7 +1604,7 @@ set_kernel_filter(pcap_t *handle, struct sock_fprog *fcode)
                char drain[1];
 
                /*
-                * Note that we've put the total socket onto the filter.
+                * Note that we've put the total filter onto the socket.
                 */
                total_filter_on = 1;
 
@@ -1637,10 +1647,20 @@ set_kernel_filter(pcap_t *handle, struct sock_fprog *fcode)
                 * we have the total filter on the socket,
                 * and it won't come off.  What do we do then?
                 */
-               setsockopt(handle->fd, SOL_SOCKET, SO_DETACH_FILTER,
-                          &dummy, sizeof(dummy));
+               reset_kernel_filter(handle);
+
                errno = save_errno;
        }
        return ret;      
 }
+
+static int
+reset_kernel_filter(pcap_t *handle)
+{
+       /* setsockopt() barfs unless it get a dummy parameter */
+       int dummy;
+
+       return setsockopt(handle->fd, SOL_SOCKET, SO_DETACH_FILTER,
+                                  &dummy, sizeof(dummy));
+}
 #endif