Folks, I've hooked up Jason's kgb/kgdb patches and been able to gather some more information about the most recent crashes on this test system. The last few crashes have occurred after starting an F12 guest, at which point __nf_conntrack_find is called with the following tuple: --- begin --- (gdb) print tuple->src->u3 $45 = {all = {16777343, 0, 0, 0}, ip = 16777343, ip6 = {16777343, 0, 0, 0}, in = {s_addr = 16777343}, in6 = {in6_u = { u6_addr8 = "\177\000\000\001", '\000' <repeats 11 times>, u6_addr16 = { 127, 256, 0, 0, 0, 0, 0, 0}, u6_addr32 = {16777343, 0, 0, 0}}}} (gdb) print tuple->src->u $46 = {all = 3607, tcp = {port = 3607}, udp = {port = 3607}, icmp = { id = 3607}, dccp = {port = 3607}, sctp = {port = 3607}, gre = {key = 3607}} (gdb) print tuple->dst $48 = {u3 = {all = {16777343, 0, 0, 0}, ip = 16777343, ip6 = {16777343, 0, 0, 0}, in = {s_addr = 16777343}, in6 = {in6_u = { u6_addr8 = "\177\000\000\001", '\000' <repeats 11 times>, u6_addr16 = { 127, 256, 0, 0, 0, 0, 0, 0}, u6_addr32 = {16777343, 0, 0, 0}}}}, u = {all = 12761, tcp = {port = 12761}, udp = {port = 12761}, icmp = { type = 217 '\331', code = 49 '1'}, dccp = {port = 12761}, sctp = { port = 12761}, gre = {key = 12761}}, protonum = 6 '\006', dir = 0 '\000'} ---end --- Which (after converting from network to host addressing) is a VNC (port 5902) TCP packet being broadcast (by the guest maybe? I didn't know Fedora started VNC by default these days, but I'll look). After looking through the netfilter code, I understand now that it maintains a hashtable (which size is computed at boot time according to system memory size, and is usually kmalloced but might be vmalloced if there is a problem - not here though). Each time a packet of interest relating to a connection we might want to track comes in, we get a "tuple" passed in to the conntrack functions, and this is hashed using hash_conntrack into an entry in an array of hlists (buckets) stored in the "ct" (conntrack) entry in the current network namespace (there is only one on this system, I checked that). In this case, when we come to look at the hashtable, it contains a number of valid entries (I looked) but not for the hashed entry calculated for this VNC packet. I would love to have advice on the best way to debug conntrack hashtable missbehavior (there's a lot of RCU use in there), especially with freeing entries. Is there more debug code I can turn on? Is there anything you guys would suggest that I look at? Jon. -- To unsubscribe from this list: send the line "unsubscribe netfilter-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html