+++ /dev/null
-LINUX KERNEL REQUIREMENTS
-=========================
-
-The linux kernel has had various major regressions, performance
-issues and subtle bugs (especially in pmtu). Here is a short list
-of some -stable kernels that have been tested (at least briefly)
-and seem to be working well with Quagga/NHRP:
- 3.12.8 or later
- 3.14.54 or later
- 3.18.22 or later[1]
- 4.4.52 or later
- 4.9.30 or later
-
-[1] But you need to apply the following two backported commits:
- 3cdaa5be9e ipv4: Don't increase PMTU with Datagram Too Big message
- cb6ccf09d6 route: Use ipv4_mtu instead of raw rt_pmtu
-
-See below for list of known issues in various kernel versions.
-
-Kernels earlier than 3.12 need CONFIG_ARPD enabled in the configuration.
-Many distributions do not enable it by default, and you may need to
-compile your own kernel.
-
-KERNEL BUGS
-===========
-
-DMVPN and mGRE support in the kernel has been brittle. There are various
-regressions in multiple kernel versions.
-
-This list tries to collect them to one source of information:
-
-- forward pmtu is disabled intentionally (but tunnel devices rely on it)
- Broken since 3.14-rc1:
- commit "ipv4: introduce ip_dst_mtu_maybe_forward and protect forwarding path against pmtu spoofing"
- Workaround:
- Set sysctl net.ipv4.ip_forward_use_pmtu=1
- (Should fix kernel to have this by default on for tunnel devices)
-
-- subtle path mtu mishandling issues
- Broken since (uncertain)
- Fixed in 4.1-rc2:
- commit "ipv4: Don't increase PMTU with Datagram Too Big message."
- commit "route: Use ipv4_mtu instead of raw rt_pmtu"
-
-- fragmentation of large packets inside tunnel not working
- Broken since 3.11-rc1
- commit "ip_tunnels: Use skb-len to PMTU check."
- Fixed in 3.14.54, 3.18.22, 4.1.9, 4.2-rc3
- commit "ip_tunnel: fix ipv4 pmtu check to honor inner ip header df"
-
-- ipsec will crash during xfrm gc
- Broke since 3.15-rc1
- commit "flowcache: Make flow cache name space aware"
- Fixed in 3.18.10, 4.0
- commit "flowcache: Fix kernel panic in flow_cache_flush_task"
-
-- TSO on GRE tunnels failed, and resulted in very slow performance
- Broke since 3.14.24, 3.18-rc3
- commit "gre: Use inner mac length when computing tunnel length"
- Fixed in 3.14.30, 3.18.4
- commit "gre: fix the inner mac header in nbma tunnel xmit path"
- commit "gre: Set inner mac header in gro complete"
-
-- NAPI GRO handling was broken; causing immediate crash (32-bit only?)
- Broken since 3.13-rc1
- commit "net: gro: allow to build full sized skb"
- Fixed 3.14.5, 3.15-rc7
- commit "net: gro: make sure skb->cb[] initial content has not to be zero"
-
-- ip_gre dst caching broke NBMA GRE tunnels
- Broken since 3.14-rc1
- Fixed in 3.14.5, 3.15-rc6
- commit "ipv4: ip_tunnels: disable cache for nbma gre tunnels"
-
-- Few packets can be lost when neighbor entry is in NUD_PROBE state,
- and there is continuous traffic to it.
- Broken since dawn of time
- Fixed in 3.15-rc1
- commit "neigh: probe application via netlink in NUD_PROBE"
-
-- GRO was implemented for GRE, but the hw capabilities were not updated
- correctly. In practice forwarding from non-GRE (physical) interface
- to GRE interface with gro/gso/tx offloads enabled (also on the target
- interface) does not work properly.
- Broken around 3.9 to 3.11, need to check details.
-
-- recvfrom() returned incorrect NBMA address, breaking NAT detection
- Broken since 3.10-rc1
- commit "GRE: Refactor GRE tunneling code."
- Fixed in 3.10.27, 3.12.8, 3.13-rc7
- commit "ip_gre: fix msg_name parsing for recvfrom/recvmsg"
-
-- sendto() was broken causing opennhrp not work at all
- Broken since 3.10-rc1
- commit "GRE: Refactor GRE tunneling code."
- Fixed in 3.10.12, 3.11-rc6
- commit "ip_gre: fix ipgre_header to return correct offset"
-
-- PMTU was broken due to GRE driver rewrite
- Broken since 3.10-rc1
- commit "GRE: Refactor GRE tunneling code."
- Fixed in 3.11-rc1
- commit "ip_tunnels: Use skb-len to PMTU check."
-
-- PMTU was broken due to routing cache removal
- Broken since 3.6-rc1
- commit "ipv4: Cache input routes in fib_info nexthops"
- Fixed in 3.11-rc1
- commit "ipv4: use next hop exceptions also for input routes"
- + 3 other commits
- Patches exist for 3.10, but they were not approved to 3.10-stable.
-
-- Race condition during bootup: changing ARP flag did not flush
- existing neighbor entries, causing problems if traffic was routed
- to gre interface before opennhrp was running.
- Broken since dawn of time
- Fixed in 3.11-rc1
- commit "arp: flush arp cache on IFF_NOARP change"
-
-- Crash in IPsec
- Broken since 3.9-rc1
- commit "xfrm: removes a superfluous check and add a statistic"
- Fixed in 3.10-rc3
- commit "xfrm: properly handle invalid states as an error"
-
-- An incorrect ip_gre change broke NHRP traffic over GRE
- Broken since 3.8-rc2
- commit "ip_gre: make ipgre_tunnel_xmit() not parse network header as IP unconditionally"
- Fixed in 3.8.5, 3.9-rc4
- commit "Revert "ip_gre: make ipgre_tunnel_xmit() not parse network header as IP unconditionally""
-
-- Multicast traffic over mGRE was broken.
- Broken since 2.6.34-rc2
- commit "gre: fix hard header destination address checking"
- Fixed in 2.6.39-rc2
- commit "net: gre: provide multicast mappings for ipv4 and ipv6"
-
-- Serious performance issues causing small throughput on medium to large DMVPN networks
- Broken since dawn of time
- Fixed in 2.6.35
- multiple commits rewriting ipsec caching
-
-- Even though around 2.6.24 is the first version where opennhrp started
- to work, there has been various PMTU, performance, and functionality
- bugs before 2.6.34. That's one of the first version I consider stable
- wrt. to opennhrp functionality.
-
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