Do MSG_PEEK call only once

[fridex]

Based on https://github.com/fridex/af_ktls/pull/28 I am open to discussion whether there can be only one peek or two peeks per kernel_recvmsg() and splice_read.

We should distinguish stream (TCP) and datagram (UDP) protocols here. As was discussed in https://github.com/fridex/af_ktls/pull/28. This should be a full list of scenarios that can happen:

• for DTLS/UDP:
  • EBADF when peeked size is bigger then we expect based on header
  • EBADF when peeked size is smaller then we expect based on header (or does not cover header at all)
  • when equal, process
• for TLS/TCP:
  • when peeked size is bigger than size based on TLS header, process only TLS record - part based on TLS header
  • when peeked size is smaller than size based on TLS header or it does not cover header at all (possibly segmented):
    • EAGAIN for nonblocking socket
    • block for blocking socket
  • when equal, proces

Can we peek only once (not a separate peek for header and then for the record)?

• for DTLS/UDP it should be pretty straight forward, since when we do the peek, the whole datagram should be already available
• for TLS/TCP:
  • since we explicitly know where is the beginning and the end of the TLS record, we could wait/report when there is not enough data
  • for nonblocking socket scenario, there can be incosistency in return value:
    1. not enough data received to handle whole record - kernel will return EAGAIN
    2. received whole record, but it was not possible to decrypt it - kernel will return EBADF (probably)
       Note this will occur even with double-peek approach

Nevertheless, peek is not a big deal though (as discussed in #28).

Any suggestions?

related: https://github.com/fridex/af_ktls/pull/28 https://github.com/fridex/af_ktls/issues/21

[djwatson]

fixed by using skb methods, closing