*strcmp(old_ip, mi->context.options.ifconfig_local) !* On Wed, Nov 19, 2025 at 9:54 AM Jon Chiappetta <[email protected]> wrote:
> 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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