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laforge gerrit-no-reply at lists.osmocom.orglaforge has posted comments on this change. ( https://gerrit.osmocom.org/c/osmo-bts/+/23814 ) Change subject: osmo-bts-trx: set don't-fragment flag on all TRXD packets ...................................................................... Patch Set 5: > Patch Set 5: > > > Patch Set 5: Code-Review-2 > > > > why that? I thought the point was to _allow_ IP fragmentation in large TRXD PDUs? You're doing the exact opposite here? > > I don't remember all the details of our previous conversation regarding the IP fragmentation, sorry. My understanding at the time of writing this patch was that we don't want the fragmentation because of the associated performance loss. It seems I understood you wrong. a) the protocol is mostly spoken over looback, where MTU is 64k b) on other interfaces, yes, we should ideally stay belwo usual MTUs such as e.g. 1500 bytes In any case, this patch doesn't solve anything. You cannot fix this potential problem with a socket option. You need to make sure in the application code, that you don't aggregate more TRXD message to exceed the "reasonable minimum MTU". If you enable the DF bit, you are actively breaking existing situations that are working for the user (with fragmentation overhead). > I did some tests with the current master (no explicit IP_MTU_DISCOVER setting), and as far as I can see, the IP fragmentation is employed by default if a TRXD PDU exceeds the MTU. So AFAIU, we want to make sure that it can be employed regardless of the system's default policy by setting IP_MTU_DISCOVER explicitly, right? If so, shall I use IP_PMTUDISC_DONT or IP_PMTUDISC_WANT? fragmentation is always enabled by default, AFAICT. So nothing needs to be done to enable it. -- To view, visit https://gerrit.osmocom.org/c/osmo-bts/+/23814 To unsubscribe, or for help writing mail filters, visit https://gerrit.osmocom.org/settings Gerrit-Project: osmo-bts Gerrit-Branch: master Gerrit-Change-Id: I25415b76b69ccf43f83ddfb0e7dd1e330fb23aa7 Gerrit-Change-Number: 23814 Gerrit-PatchSet: 5 Gerrit-Owner: fixeria <vyanitskiy at sysmocom.de> Gerrit-Reviewer: Jenkins Builder Gerrit-Reviewer: laforge <laforge at osmocom.org> Gerrit-Comment-Date: Tue, 26 Oct 2021 15:23:34 +0000 Gerrit-HasComments: No Gerrit-Has-Labels: No Gerrit-MessageType: comment -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.osmocom.org/pipermail/gerrit-log/attachments/20211026/e288697e/attachment.htm>