ltp: fix af_alg02 to specify control data

It isn't clearly defined what happens if you read from an AF_ALG request socket without previously sending the control data to begin an encryption or decryption operation. On some kernels the read will return 0, while on others it will block.

Testing this corner case isn't the purpose of af_alg02; it just wants to try to encrypt a zero-length message. So, change it to explicitly send a zero-length message with control data.

This fixes the test failure reported at
https://lkml.kernel.org/r/CA+G9fYtebf78TH-XpqArunHc1L6s9mHdLEbpY1EY9tSyDjp=sg@mail.gmail.com

Fixing the test in this way was also previously suggested at
https://lkml.kernel.org/r/[email protected]

Note, this patch doesn't change the fact that the read() still blocks on pre-4.14 kernels (which is a kernel bug), and thus the timeout logic in the test is still needed.

Eric Biggers (2):
lib/tst_af_alg: add tst_alg_sendmsg() crypto/af_alg02: send message with control data before reading

 include/tst_af_alg.h               | 32 +++++++++++++++
 lib/tst_af_alg.c                   | 64 ++++++++++++++++++++++++++++++
 testcases/kernel/crypto/af_alg02.c | 21 ++++++++--
 3 files changed, 114 insertions(+), 3 deletions(-)

2.28.0