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Date: Mon, 24 Jul 2017 20:52:01 +0000 From: bugzilla-dae...@bugzilla.kernel.org To: step...@networkplumber.org Subject: [Bug 196469] New: UDPv4+UDPv6 receive silently fails after heavy UDP load https://bugzilla.kernel.org/show_bug.cgi?id=196469 Bug ID: 196469 Summary: UDPv4+UDPv6 receive silently fails after heavy UDP load Product: Networking Version: 2.5 Kernel Version: 4.12.2 Hardware: All OS: Linux Tree: Mainline Status: NEW Severity: normal Priority: P1 Component: IPV4 Assignee: step...@networkplumber.org Reporter: cfswo...@gmail.com Regression: No I have a system that's performing heavy SNMP monitoring on various devices over IPv6. After upgrading it from 4.11.5 to 4.12.2 last week, I noticed this weekend that all UDP packets received by the system were being silently dropped. The problem happened this weekend, after the system had been running for about 2 days with no issue, and without any human intervention at the time (i.e. it broke on its own - no configuration changes were made). I verified UDP replies were coming in via tcpdump, and checked netfilter and conntrack to make sure nothing was blocking it (indeed netfilter/conntrack is able to see the traffic, indicating the problem is deeper in the network stack). There is no relevant or even unusual output whatsoever in dmesg. This affects ALL received UDPv4/UDPv6 packets, even traffic on a loopback interface: opening a pair of Python sessions and trying to send UDP traffic back and forth on 127.0.0.1 results in the traffic getting dropped as well. ICMP and TCP are unaffected. My gut says it's a race condition somewhere in the UDP receive queue(s). What puzzles me is why heavy UDPv6 load caused the kernel to shut out all UDPv4 traffic too. -- You are receiving this mail because: You are the assignee for the bug.
