1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
|
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 and the first point release that is supposedly
working well with opennhrp/dmvpn:
3.12.8 or later
3.14.54 or later
3.18.22 or later[1]
[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.
|
