On Mon, 2017-04-10 at 09:26 -0600, David Ahern wrote: > On 4/8/17 2:24 PM, Johannes Berg wrote: > > @@ -2300,14 +2332,35 @@ void netlink_ack(struct sk_buff *in_skb, > > struct nlmsghdr *nlh, int err) > > NLMSG_ERROR, payload, 0); > > errmsg = nlmsg_data(rep); > > errmsg->error = err; > > - memcpy(&errmsg->msg, nlh, payload > sizeof(*errmsg) ? nlh- > > >nlmsg_len : sizeof(*nlh)); > > + memcpy(&errmsg->msg, nlh, > > + !(nlk->flags & NETLINK_F_CAP_ACK) ? nlh->nlmsg_len > > + : sizeof(*nlh)); > > + > > generically this makes userspace parsing more problematic: the > parsing layer may not know if the socket option has been set to > precisely know the size of errmsg->msg and how much data needs to be > skipped to get to the new attributes. Yes, I know. I'd hope that userspace can remember that per socket - I don't see a good other way to do this. If we insert the TLVs in front of, or instead of (with a TLV containing it), the request message then at least libnl's debugging will need to be changed. As it is, I can assume that libnl will not set the CAP setting, and everything works fine even if I don't change libnl, which makes things easier. Do you have any better ideas? johannes
