tcpdump mailing list archives

Re: Current wireless-testing breaks libpcap: mr_alen should be set


From: Guy Harris <guy () alum mit edu>
Date: Sat, 6 Mar 2010 13:23:12 -0800


On Mar 2, 2010, at 5:00 PM, Pavel Roskin wrote:

This patch to libpcap helps:

--- a/pcap-linux.c
+++ b/pcap-linux.c
@@ -1563,6 +1563,7 @@ live_open_new(pcap_t *handle, const char
                      memset(&mr, 0, sizeof(mr));
                      mr.mr_ifindex = handle->md.ifindex;
                      mr.mr_type    = PACKET_MR_PROMISC;
+                     mr.mr_alen    = 6;

If there are any network types that support promiscuous mode and have link-layer addresses that aren't 6 octets long, 
that would still fail.

It sounds as if the fix is not to care about the address length if the address isn't used, so you don't need to get the 
length right for PACKET_MR_PROMISC or PACKET_MR_ALLMULTI, so libpcap, and other clients setting promiscuous or "show me 
all multicast packets" mode, don't need to change.  Is that the case?
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