fix: Use cgroup_skb programs for payload inspection #226
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Before this change, we were using LSM programs attached to `sock_recvmsg` and `sock_sendmsg` hooks for this purpose. We were using `iov_iter` to read the payload. Unfortunately, torvalds/linux@747b1f6 (which landed in kernel 6.4) broke the `iov_iter` API in completely backwards-incompatible way, which can't be handled by any of CO-RE helpers while using an `iov_iter` definition from any kernel. Initially, we aimed to handle this incompatibility by introducing a pre-6.4 compat header and trying to cast the types (exein-io#198). That seemed to work, but unfortunately, verifiers in 5.x kernels are unhappy about this solution. Therefore, this change drops the idea of intercepting payloads with LSM all together and instead uses cgroup_skb for the same purpose. There is no way `__sk_buff` is going to introduce any breaking changes in regards to accessing the packet data.
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banditopazzo
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Dec 11, 2023
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Before this change, we were using LSM programs attached to
sock_recvmsgandsock_sendmsghooks for this purpose. We were usingiov_iterto read the payload.Unfortunately, torvalds/linux@747b1f6 (which landed in kernel 6.4) broke the
iov_iterAPI in completely backwards-incompatible way, which can't be handled by any of CO-RE helpers while using aniov_iterdefinition from any kernel.Initially, we aimed to handle this incompatibility by introducing a pre-6.4 compat header and trying to cast the types (#198). That seemed to work, but unfortunately, verifiers in 5.x kernels are unhappy about this solution.
Therefore, this change drops the idea of intercepting payloads with LSM all together and instead uses cgroup_skb for the same
purpose. There is no way
__sk_buffis going to introduce any breaking changes in regards to accessing the packet data.