lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
Open Source and information security mailing list archives
| ||
|
Message-Id: <20230517042757.161832-1-kuifeng@meta.com> Date: Tue, 16 May 2023 21:27:55 -0700 From: Kui-Feng Lee <thinker.li@...il.com> To: netdev@...r.kernel.org, ast@...nel.org, martin.lau@...ux.dev, kernel-team@...a.com Cc: Kui-Feng Lee <kuifeng@...a.com> Subject: [RFC PATCH net-next 0/2] Mitigate the Issue of Expired Routes in Linux IPv6 Routing Tables The size of a Linux IPv6 routing table can become a big problem if not managed appropriately. Now, Linux has a garbage collector to remove expired routes periodically. However, this may lead to a situation in which the routing path is blocked for a long period due to an excessive number of routes. For example, years ago, there is a commit about "ICMPv6 Packet too big messages". The root cause is that malicious ICMPv6 packets were sent back for every small packet sent to them. These packets have to lookup/insert a new route, putting hosts under high stress due to contention on a spinlock while one is stuck in fib6_run_gc(). Why Route Expires ================= Users can add IPv6 routes with an expiration time manually. However, the Neighbor Discovery protocol may also generate routes that can expire. For example, Router Advertisement (RA) messages may create a default route with an expiration time. [RFC 4861] For IPv4, it is not possible to set an expiration time for a route, and there is no RA, so there is no need to worry about such issues. Create Routes with Expires ========================== You can create routes with expires with the command. For example, ip -6 route add 2001:b000:591::3 via fe80::5054:ff:fe12:3457 \ dev enp0s3 expires 30 The route that has been generated will be deleted automatically in 30 seconds. GC of FIB6 ========== The function called fib6_run_gc() is responsible for performing garbage collection (GC) for the Linux IPv6 stack. It checks for the expiration of every route by traversing the tries of routing tables. The time taken to traverse a routing table increases with its size. Holding the routing table lock during traversal is particularly undesirable. Therefore, it is preferable to keep the lock for the shortest possible duration. Solution ======== The cause of the issue is keeping the routing table locked during the traversal of large tries. To address this, the patchset eliminates garbage collection that does the tries traversal and introduces individual timers for each route that eventually expires. Walking trials are no longer necessary with the timers. Additionally, the time required to handle a timer is consistent. If the expiration time is long, the timer becomes less precise. The drawback is that the longer the expiration time, the less accurate the timer. Kui-Feng Lee (2): net: Remove expired routes with separated timers. net: Remove unused code and variables. include/net/ip6_fib.h | 21 ++--- include/net/ip6_route.h | 2 - include/net/netns/ipv6.h | 6 -- net/ipv6/addrconf.c | 8 +- net/ipv6/ip6_fib.c | 160 ++++++++++++++++++--------------------- net/ipv6/ndisc.c | 4 +- net/ipv6/route.c | 119 ++--------------------------- 7 files changed, 95 insertions(+), 225 deletions(-) -- 2.34.1
Powered by blists - more mailing lists