On Tue, 4 Oct 2016, Justin Piszcz wrote:
> kernel 4.8 with ulogd-2.0.5- IPs are no longer logged:
>
> Oct 4 17:51:30 atom INPUT_BLOCK IN=eth1 OUT=
> MAC=00:1b:21:9c:3b:fa:3e:94:d5:d2:49:1e:08:00 LEN=0 TOS=00 PREC=0x00
> TTL=0 ID=0 PROTO=0 MARK=0
> Oct 4 17:51:31 atom INPUT_BLOCK IN=eth1 OUT=
> MAC=00:1b:21:9c:3b:fa:3e:94:d5:d2:49:1e:08:00 LEN=0 TOS=00 PREC=0x00
> TTL=0 ID=0 PROTO=0 MARK=0
> Oct 4 17:51:32 atom INPUT_BLOCK IN=eth1 OUT=
> MAC=00:1b:21:9c:3b:fa:3e:94:d5:d2:49:1e:08:00 LEN=0 TOS=00 PREC=0x00
> TTL=0 ID=0 PROTO=0 MARK=0
>
> (reboot back to kernel 4.7, works fine)
>
> kernel 4.7 with ulogd-2.0.5:
> Oct 4 17:56:44 atom INPUT_BLOCK IN=eth1 OUT=
> MAC=00:1b:21:9c:3b:fa:3e:94:d5:d2:49:1e:08:00 SRC=74.125.22.125
> DST=1.2.3.4 LEN=397 TOS=00 PREC=0x00 TTL=48 ID=58093 PROTO=TCP
> SPT=5222 DPT=19804 SEQ=2032644254 ACK=2273184383 WINDOW=55272 ACK PSH
> URGP=0 MARK=0
> Oct 4 17:56:45 atom INPUT_BLOCK IN=eth1 OUT=
> MAC=00:1b:21:9c:3b:fa:3e:94:d5:d2:49:1e:08:00 SRC=74.125.22.125
> DST=1.2.3.4 LEN=397 TOS=00 PREC=0x00 TTL=48 ID=58725 PROTO=TCP
> SPT=5222 DPT=19804 SEQ=2032644254 ACK=2273184383 WINDOW=55272 ACK PSH
> URGP=0 MARK=0
>
> Looks like there were some changes in the 4.8 kernel regarding ulogd,
> has anyone else run into this problem?
For me, kernel 4.8.1 results in segfaults in ulogd-2.0.5 at:
Program received signal SIGSEGV, Segmentation fault.
0x00007ffff65fd18a in _interp_iphdr (pi=0x617f50, len=0) at
ulogd_raw2packet_BASE.c:720
715 static int _interp_iphdr(struct ulogd_pluginstance *pi, uint32_t len)
716 {
717 struct ulogd_key *ret = pi->output.keys;
718 struct iphdr *iph =
719 ikey_get_ptr(&pi->input.keys[INKEY_RAW_PCKT]);
720 void *nexthdr = (uint32_t *)iph + iph->ihl;
I believe 7643507fe8b5bd8ab7522f6a81058cc1209d2585 changed previous
behavior by not always copying IP header data to user space.
On my machine IPv4 log packets result in a ulogd segfault while IPv6
packets do not. I'm not sure of the cause of the difference.
The corresponding userspace commit for the 209d2585 kernel change is:
https://git.netfilter.org/iptables/commit/?id=7070b1f3c88a0c3d4e315c00cca61f05b0fbc882
This adds --nflog-size to iptables. When --nflog-size is used with my
iptables NFLOG lines, the ulogd-2.0.5 segfaults cease.
I'm surprised to see a kernel change cause unexpected userspace segfaults,
so further investigation into a kernel fix would seem a good idea.
Having to add the likes of "--nflog-size 200" (200 simply being what I am
using) to every NFLOG line in firewall configs is a significant burden for
many.
Putting out a new release of iptables may help ease this transition if the
kernel is not patched to fix this. I had to use the git code since 1.6.0
doesn't have it.
Chris
