Hi, I noticed that MLDv2 Reports don't seem to have a default skb->mark of 0. Instead it is 212 / 0xd4 for me: ``` $ ip link add dummy0 type dummy $ ip link set up dummy0 arp on $ ip6tables -I INPUT -i dummy0 -j LOG --log-ip-options [ send an MLDv2 Query, for instance via the ipv6toolkit https://github.com/T-X/ipv6toolkit/tree/pr-mldq6-mldv2 ] $ dmesg ... [38336.524879] IN= OUT=dummy0 SRC=fe80:0000:0000:0000:1c01:1cff:fec1:5669 DST=ff02:0000:0000:0000:0000:0000:0000:0016 LEN=76 TC=0 HOPLIMIT=1 FLOWLBL=0 OPT ( ) PROTO=ICMPv6 TYPE=143 CODE=0 MARK=0xd4 ... ``` For MLDv1 Reports I don't see this issue, there it's always 0 by default. I'm wondering if this 212 value comes from the skb->reserved_tailroom (formerly avail_size) which the skb->mark is unioned with? Am I reading a21d45726a ("tcp: avoid order-1 allocations on wifi and tx path") correctly that the IPv6 stack should have reset skb->mark to 0 before transmission? Initially observed on a Linux 5.10.184. But I can reproduce this on a Linux 6.3.7, too. Regards, Linus
