netdev - [PATCH v2 ipsec 0/2] xfrm: Fix bugs in stacked XFRM-I tunnels

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Date:   Wed, 24 Aug 2022 22:12:50 +0000
From:   Benedict Wong <benedictwong@...gle.com>
To:     steffen.klassert@...unet.com, netdev@...r.kernel.org
Cc:     nharold@...gle.com, benedictwong@...gle.com, lorenzo@...gle.com
Subject: [PATCH v2 ipsec 0/2] xfrm: Fix bugs in stacked XFRM-I tunnels

This patch set fixes bugs that prevent stacked IPsec tunnels (via XFRM
interfaces) from receiving packets properly. The apparent cause of the
issues is that the inner tunnel’s policy checks fail to validate the
outer tunnel’s secpath entries (since it no longer has a reference to
the outer tunnel policies, and each call validates ALL secpath entries)
before verifying the inner tunnel’s. This fixes this by caching the list
of verified secpath entries, and skipping them upon future validation
runs.

PATCH 1/2 Makes template matching for previously verified entries in the
secpath an optional match. This ensures that lost context for previous
tunnel secpath entries does not trigger a template mismatch if it was
previously verified. This allows each tunnel layer to incrementally
verify only the secpath entries associated with it.

PATCH 2/2 Ensures that policies for nested tunnel mode transforms are
verified (and marked as such) before additional decapsulation. This
ensures that entries in the secpath are verified while the context
(intermediate IP addresses, marks, etc) can be appropriately matched.
Notably, unencapsulated ESP did not perform policy checks before handing
to the next protocol for processing.

v1 -> v2:
- Reordered and rescoped patches to make changes clearer; policy
    check in xfrm_input necessary due to the incremental-verification
    process.
- Code style updates to conform with networking code formatting
- No net functional changes across both patches.