[dpdk-dev] [PATCH v2 4/6] net/pcap: add libpcap wrappers

[Dmitry Kozlyuk]

2021-03-01 21:43, Nick Connolly:
> > Complete removal of non-standard dependencies in headers is within a grasp.
> > Then we can remove shims and include whatever needed.
> > Thoughts?
> Sounds good. A couple of 'gotchas' that I've come across (but may not be 
> an issue for DPDK):
> 
>   * Memory allocation / free that spans a dll boundary (see earlier email).

Not sure which email you mean, could you give a link?

>   * posix_memalign is unfortunately specified as using free(), so we'll
>     either have to modify the calls to rte_posix_memalign /
>     rte_free_memalign (which means code analysis to find which free
>     calls need changing), or wrapper free() to distinguish the two types
>     of memory somehow. I 'solved' this for SPDK by using posix_memalign
>     for everything and I have a vague recollection that the mingw libc
>     does something similar.

Is posix_memalign() used more extensively in SPDK? In DPDK, it's 2 PMDs:
  * mlx5 PMD uses _aligned_malloc/_aligned_free on Windows;
  * dpaax (PMD family) uses posix_memalign() to allocate pages.
There are "malloc" and "alloc_size" attributes that can help code analysis.

>   * Sockets are unfortunately specified as using close(). This is
>     probably easy to address by rte_ wrapping all socket calls.

Which public DPDK APIs operate on sockets?
I don't like the idea of wrapping APIs like sockets or files.
(Yes, we're discussing libpcap API wrappers in this thread, but we already
agreed they are a mistake and they were internal in the first place.)

I drafted what I was talking about: adding address types and removing shims:

* librte_net/rte_ip.h then includes <netinet/ip.h> or <ws2tcpip.h>
  conditionally for AF_xxx, IPPROTO_xxx, and a few other constants.
  That's probably OK, there are similar places for Linux/FreeBSD differences,
  e.g. in <rte_endian.h>.

* Some IPPROTO_xxx constants are missing on Windows, so rte_ip.h has to
  provide them. I hope Mirosoft will add them to system headers one day.

* It affects cmdline (mostly), ethdev, security, crypto/dpaax.