Branch: refs/heads/pmtud-fixes Home: https://github.com/kronosnet/kronosnet Commit: 434299300a2f23acd96f2f287939549ab2944411 https://github.com/kronosnet/kronosnet/commit/434299300a2f23acd96f2f2879395… Author: Fabio M. Di Nitto <fdinitto(a)redhat.com> Date: 2019-08-13 (Tue, 13 Aug 2019) Changed paths: M libknet/internals.h M libknet/links.c M libknet/links.h M libknet/threads_pmtud.c Log Message: ----------- [PMTUd] add dynamic pong timeout when using crypto problem originally reported by proxmox community, users observed that under pressure the MTU would flap back and forth between 2 values due to other node response timeout. implement a dynamic timeout multiplier when using crypto that should solve the problem in a more flexible fashion. When a timeout hits, those new logs will show: [knet]: [info] host: host: 1 (passive) best link: 0 (pri: 0) [knet]: [debug] pmtud: Starting PMTUD for host: 1 link: 0 [knet]: [debug] pmtud: Increasing PMTUd response timeout multiplier to (4) for host 1 link: 0 [knet]: [info] pmtud: PMTUD link change for host: 1 link: 0 from 469 to 65429 [knet]: [debug] pmtud: PMTUD completed for host: 1 link: 0 current link mtu: 65429 [knet]: [info] pmtud: Global data MTU changed to: 65429 [knet]: [debug] pmtud: Starting PMTUD for host: 1 link: 0 [knet]: [debug] pmtud: Increasing PMTUd response timeout multiplier to (8) for host 1 link: 0 [knet]: [debug] pmtud: Increasing PMTUd response timeout multiplier to (16) for host 1 link: 0 [knet]: [debug] pmtud: Increasing PMTUd response timeout multiplier to (32) for host 1 link: 0 [knet]: [debug] pmtud: Increasing PMTUd response timeout multiplier to (64) for host 1 link: 0 [knet]: [debug] pmtud: PMTUD completed for host: 1 link: 0 current link mtu: 65429 [knet]: [debug] pmtud: Starting PMTUD for host: 1 link: 0 [knet]: [debug] pmtud: Increasing PMTUd response timeout multiplier to (128) for host 1 link: 0 [knet]: [debug] pmtud: PMTUD completed for host: 1 link: 0 current link mtu: 65429 and when the latency reduces and it is safe to be more responsive again: [knet]: [debug] pmtud: Starting PMTUD for host: 1 link: 0 [knet]: [debug] pmtud: Decreasing PMTUd response timeout multiplier to (64) for host 1 link: 0 [knet]: [debug] pmtud: PMTUD completed for host: 1 link: 0 current link mtu: 65429 .... testing this patch on normal hosts is a bit challenging tho. Patch was tested by hardcoding a super low timeout here: diff --git a/libknet/threads_pmtud.c b/libknet/threads_pmtud.c index 4f0ba0f..5e2b89b 100644 --- a/libknet/threads_pmtud.c +++ b/libknet/threads_pmtud.c @@ -261,7 +271,8 @@ retry: /* * crypto, under pressure, is a royal PITA */ - pong_timeout_adj_tmp = dst_link->pong_timeout_adj * 2; + //pong_timeout_adj_tmp = dst_link->pong_timeout_adj * dst_link->pmtud_crypto_timeout_multiplier; + pong_timeout_adj_tmp = 30 * dst_link->pmtud_crypto_timeout_multiplier; } else { pong_timeout_adj_tmp = dst_link->pong_timeout_adj; } and using a long running version of api_knet_send_crypto_test with a short PMTUd setfreq (10 sec). Signed-off-by: Fabio M. Di Nitto <fdinitto(a)redhat.com>