Hi Gert, Yes, that is correct, it does impact the multi-threaded operation, however, the older logic has a strcmp between the old IP and the new IP before performing the learn and unlearn logic in the update_vhash function which is what SHOULD happen, this is important and correct. Why would you want to waste cycles and operations doing that when the IPs haven't even changed or differed in value? It doesn't make any logical sense either way even in single threaded operation...
Thanks, Jon C On Wed, Nov 19, 2025 at 9:43 AM Gert Doering <[email protected]> wrote: > Hi, > > On Wed, Nov 19, 2025 at 09:19:35AM -0500, Jon Chiappetta via Openvpn-devel > wrote: > > This is something I noticed recently with potential connection > > interruptions which could occur which the original older code checked > for! > > > > https://github.com/OpenVPN/openvpn/pull/910 > > Yeah, but, no. > > Since our code is single-threaded, there is no time frame between > "unlearn" and "relearn" where a packet could come in and be dropped, due > to "address not known". > > So yes, on a PUSH_UPDATE with "the same ifconfig again", we do more work > than we would have to do, but it has no adverse effects - and if you are > worried about that, then do not send PUSH_UPDATE with unchanged configs > (given that the client would do a full tun restart on receiving > PUSH_UPDATE, > this has way more impact than on the server). > > > > There was an update pushed earlier this year which undid some important > > logic in terms of learning/unlearning the ifconfig IP address. The older > > original code would check that the new/old IPs don't match first before > > performing that logic. I believe this was important and correct because > it > > could cause connection interruptions during the learn/unlearn process if > > the IP address has stayed the same! > > The older code did not do proper unlearning at all, so was obviously not > correct. > > gert > -- > "If was one thing all people took for granted, was conviction that if you > feed honest figures into a computer, honest figures come out. Never > doubted > it myself till I met a computer with a sense of humor." > Robert A. Heinlein, The Moon is a Harsh > Mistress > > Gert Doering - Munich, Germany > [email protected] >
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