[openssl-dev] AF_ALG engine support and kernel versions

[Jeffrey Walton]

Hi Everyone,

Looking at the code in engines/afalg/e_afalg.c, there is the following:

  ...
  #define K_MAJ   4
  #define K_MIN1  1
  #define K_MIN2  0
  #if LINUX_VERSION_CODE <= KERNEL_VERSION(K_MAJ, K_MIN1, K_MIN2)
  # warning "AFALG ENGINE requires Kernel Headers >= 4.1.0"
  # warning "Skipping Compilation of AFALG engine"
  #else
  ...

It appears AF_ALG was added to the kernel at 2.6.38. Asynchronous I/O
support appears to have surfaced in the kernel at 2.5.23.

Where is the requirement for 4.1 coming from?

Also, "Fixing asynchronous I/O, again", dated January 2016
(http://lwn.net/Articles/671649/) could explain why later 4.x kernels
are having problems with the afalgtest.

Jeff