OpenBSD: add sendmmsg and recvmmsg support.

[devnexen]

close #3696

[rustbot]

r? @JohnTitor

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[rustbot]

Some changes occurred in OpenBSD module

cc @semarie

[semarie]

it doesn't pass the test suite under OpenBSD.

  cargo:warning=/data/semarie/repos/rust/build-libc/build/x86_64-unknown-openbsd/debug/build/libc-test-29cac031f36c8215/out/main.c:15544:51: error: must use 'struct' tag to refer to type 'mmsghdr'
  cargo:warning=             int (*__test_fn_sendmmsg(void))(int, mmsghdr*, unsigned int, int) {
  cargo:warning=                                                  ^
  cargo:warning=                                                  struct
  cargo:warning=/data/semarie/repos/rust/build-libc/build/x86_64-unknown-openbsd/debug/build/libc-test-29cac031f36c8215/out/main.c:15549:51: error: must use 'struct' tag to refer to type 'mmsghdr'
  cargo:warning=             int (*__test_fn_recvmmsg(void))(int, mmsghdr*, unsigned int, int, struct timespec*) {
  cargo:warning=                                                  ^
  cargo:warning=                                                  struct
  cargo:warning=2 errors generated.

  --- stderr
  rust version: 1.80.0


  error occurred: Command "/usr/local/bin/sccache" "cc" "-O0" "-ffunction-sections" "-fdata-sections" "-fPIC" "-gdwarf-2" "-fno-omit-frame-pointer" "-m64" "--target=x86_64-unknown-openbsd" "-Wall" "-Wextra" "-Wall" "-Wextra" "-Werror" "-Wno-unused-parameter" "-Wno-type-limits" "-Wno-address-of-packed-member" "-Wno-unknown-warning-option" "-Wno-deprecated-declarations" "-Wno-deprecated-declarations" "-o" "/data/semarie/repos/rust/build-libc/build/x86_64-unknown-openbsd/debug/build/libc-test-29cac031f36c8215/out/08e68c28a9818392-main.o" "-c" "/data/semarie/repos/rust/build-libc/build/x86_64-unknown-openbsd/debug/build/libc-test-29cac031f36c8215/out/main.c" with args cc did not execute successfully (status code exit status: 1).

[semarie]

LGTM now (but getnameinfo break the build)

[tgross35]

This is follow up of #3703

[tgross35]

Could you add sendmmsg and mmsghdr?

[tgross35]

OpenBSD and NetBSD actually seem to have a slightly different signature for sendmmsg: on OpenBSD the mmsg pointer is const, but not for NetBSD. I assume NetBSD could also be const even though this isn't in the API.

This doesn't seem worth special casing on, leaving it mut does work for both. So LGTM, thanks!

• https://man.openbsd.org/sendmsg.2
• https://man.netbsd.org/NetBSD-7.0/sendmmsg.2.