I am doing egress logging on my server using IPTABLES with the following line which is supposed to provide UID information on all traffic that is logged:
-A OUTPUT -j LOG --log-prefix "IPTABLES(O): " --log-level info --log-uid
However, once in a while, I would get logs without UID like this:
IPTABLES(O): IN= OUT=eth0 SRC=220.127.116.11 DST=18.104.22.168 LEN=83 TOS=0x00 PREC=0x00 TTL=64 ID=54321 DF PROTO=TCP SPT=50505 DPT=443 WINDOW=342 RES=0x00 ACK PSH FIN URGP=0
What are the reasons for outgoing traffic to not contain any UID information?