mirror of
https://github.com/AuxXxilium/linux_dsm_epyc7002.git
synced 2024-11-30 23:36:44 +07:00
b3c6efbc36
Create Documentation/networking/ipsec.txt to document IPsec corner issues and other info, which will be useful when user deploying IPsec. Signed-off-by: Fan Du <fan.du@windriver.com> Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
39 lines
1.8 KiB
Plaintext
39 lines
1.8 KiB
Plaintext
|
|
Here documents known IPsec corner cases which need to be keep in mind when
|
|
deploy various IPsec configuration in real world production environment.
|
|
|
|
1. IPcomp: Small IP packet won't get compressed at sender, and failed on
|
|
policy check on receiver.
|
|
|
|
Quote from RFC3173:
|
|
2.2. Non-Expansion Policy
|
|
|
|
If the total size of a compressed payload and the IPComp header, as
|
|
defined in section 3, is not smaller than the size of the original
|
|
payload, the IP datagram MUST be sent in the original non-compressed
|
|
form. To clarify: If an IP datagram is sent non-compressed, no
|
|
|
|
IPComp header is added to the datagram. This policy ensures saving
|
|
the decompression processing cycles and avoiding incurring IP
|
|
datagram fragmentation when the expanded datagram is larger than the
|
|
MTU.
|
|
|
|
Small IP datagrams are likely to expand as a result of compression.
|
|
Therefore, a numeric threshold should be applied before compression,
|
|
where IP datagrams of size smaller than the threshold are sent in the
|
|
original form without attempting compression. The numeric threshold
|
|
is implementation dependent.
|
|
|
|
Current IPComp implementation is indeed by the book, while as in practice
|
|
when sending non-compressed packet to the peer(whether or not packet len
|
|
is smaller than the threshold or the compressed len is large than original
|
|
packet len), the packet is dropped when checking the policy as this packet
|
|
matches the selector but not coming from any XFRM layer, i.e., with no
|
|
security path. Such naked packet will not eventually make it to upper layer.
|
|
The result is much more wired to the user when ping peer with different
|
|
payload length.
|
|
|
|
One workaround is try to set "level use" for each policy if user observed
|
|
above scenario. The consequence of doing so is small packet(uncompressed)
|
|
will skip policy checking on receiver side.
|