I captured the following traces and will comment inline on what I could find:
Starting with a client running on Linux 6.6.13, trying to access /afs/desy.de: fstrace: https://homepages.upb.de/lass/openafs/6.6.13.fstrace pcapng: https://homepages.upb.de/lass/openafs/6.6.13.pcapng The packet trace (pcapng, can be opened with Wireshark) shows that the reply to fetch-data-64 (i.e., the directory listing) arrives in fragments (e.g., frames 127+128). Nevertheless, the reception of the packet is acknowledged in frame 131. In the end, everything works fine. Running the same scenario on Linux 6.7: fstrace: https://homepages.upb.de/lass/openafs/6.7_default-mtu_default-rxmaxmtu.fstrace pcapng: https://homepages.upb.de/lass/openafs/6.7_default-mtu_default-rxmaxmtu.pcapng The receiving side looks very similar, we still receive the reply to fetch-data-64 in fragments (frames 127+128, 129+130, etc.). However, the reception is never acknowledged by the client. The getdents64 syscall hangs forever. Reducing the maximum RX MTU via -rxmaxmtu 1400 on Linux 6.7: fstrace: https://homepages.upb.de/lass/openafs/6.7_default-mtu_rxmtu-1400.fstrace pcapng: https://homepages.upb.de/lass/openafs/6.7_default-mtu_rxmaxmtu-1400.pcapng The reply to fetch-data-64 is not fragmented anymore because the RX packets are sufficiently small (frames 149-152). The reception is ACK'd in frame 154. It could be that the larger UDP packets are segmented by my provider, as my IPv4 connection is realized via DS-Lite (a carrier-grade NAT [1][2]), which may reduce the MTU. This segmentation may be key to reproduce this issue. Still, it worked fine with Linux 6.6, even when receiving fragmented responses, and it is not working anymore with Linux 6.7. I may start bisecting the Linux kernel changes between 6.6 and 6.7, but I fear that this will take weeks... Best regards, Michael [1] https://en.wikipedia.org/wiki/Carrier-grade_NAT [2] https://en.wikipedia.org/wiki/IPv6_transition_mechanism#Dual-Stack_Lite_(DS-Lite) _______________________________________________ OpenAFS-devel mailing list OpenAFS-devel@openafs.org https://lists.openafs.org/mailman/listinfo/openafs-devel
