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In-Reply-To: <20240508180946.47e6610a@kernel.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 09/05/2024 03:09, Jakub Kicinski wrote: > On Wed, 8 May 2024 11:49:07 +0200 Antonio Quartulli wrote: >>>> + netdev_err(dev, "%s: cannot add ifname to reply\n", __func__); >>> >>> Probably not worth it, can't happen given the message size >> >> Personally I still prefer to check the return value of functions that >> may fail, because somebody may break the assumption (i.e. message large >> enough by design) without realizing that this call was relying on that. >> >> If you want, I could still add a comment saying that we don't expect >> this to happen. > > In a few other places we put a WARN_ON_ONCE() on messages size errors. > That way syzbot usually catches the miscalculation rather quickly. > But no strong objections if you prefer the print. I am fine as long as we have some check. If WARN_ON_ONCE() helps syzbot, then I'll go with it. > >>>> + genlmsg_cancel(msg, hdr); >>>> + nlmsg_free(msg); >>>> + return -EMSGSIZE; >>>> + } >>>> + >>>> + genlmsg_end(msg, hdr); >>>> + >>>> + return genlmsg_reply(msg, info); >>>> } >>>> >>>> int ovpn_nl_del_iface_doit(struct sk_buff *skb, struct genl_info *info) >>>> { >>>> - return -ENOTSUPP; >>>> + struct ovpn_struct *ovpn = info->user_ptr[0]; >>>> + >>>> + rtnl_lock(); >>>> + ovpn_iface_destruct(ovpn); >>>> + dev_put(ovpn->dev); >>>> + rtnl_unlock(); >>>> + >>>> + synchronize_net(); >>> >>> Why? 🤔️ >> >> >> hmm I was under the impression that we should always call this function >> when destroying an interface to make sure that packets that already >> entered the network stack can be properly processed before the interface >> is gone for good. >> >> Maybe this is not the right place? Any hint? > > The unregistration of the netdevice should take care of syncing packets > in flight, AFAIU. I have another call to synchronize_net() in ovpn_iface_destruct() after calling unregister_netdevice(). Sabrina was actually questioning that call too. First of all I now realize that we are calling it twice, but from what I am understanding, I think we can just ditch any invocation and let core do the right thing. I'll remove it and do some tests. -- Antonio Quartulli OpenVPN Inc.