add getprotobyname (#15273)

* add getprotobyname

* tests, docs, changelog

* add since

lib/pure/nativesockets.nim

@@ -13,6 +13,8 @@
 # TODO: Clean up the exports a bit and everything else in general.
 
 import os, options
+import std/private/since
+
 
 when hostOS == "solaris":
   {.passl: "-lsocket -lnsl".}
@@ -199,6 +201,18 @@ proc toSockType*(protocol: Protocol): SockType =
   of IPPROTO_IP, IPPROTO_IPV6, IPPROTO_RAW, IPPROTO_ICMP, IPPROTO_ICMPV6:
     SOCK_RAW
 
+proc getProtoByName*(name: string): int {.since: (1, 3, 5).} =
+  ## Returns a protocol code from the database that matches the protocol ``name``.
+  when useWinVersion:
+    let protoent = winlean.getprotobyname(name.cstring)
+  else:
+    let protoent = posix.getprotobyname(name.cstring)
+  
+  if protoent == nil:
+    raise newException(OsError, "protocol not found")
+
+  result = protoent.p_proto.int
+
 proc close*(socket: SocketHandle) =
   ## Closes a socket.
   when useWinVersion:

lib/windows/winlean.nim

@@ -96,6 +96,12 @@ type
     dwPlatformId*: DWORD
     szCSDVersion*: array[0..127, WinChar]
 
+  Protoent* = object
+    p_name*: cstring
+    p_aliases*: cstringArray
+    p_proto*: cshort
+
+
 const
   STARTF_USESHOWWINDOW* = 1'i32
   STARTF_USESTDHANDLES* = 256'i32
@@ -573,6 +579,14 @@ proc gethostbyname*(name: cstring): ptr Hostent {.
 proc gethostname*(hostname: cstring, len: cint): cint {.
   stdcall, importc: "gethostname", dynlib: ws2dll, sideEffect.}
 
+proc getprotobyname*(
+  name: cstring
+): ptr Protoent {.stdcall, importc: "getprotobyname", dynlib: ws2dll, sideEffect.}
+
+proc getprotobynumber*(
+  proto: cint
+): ptr Protoent {.stdcall, importc: "getprotobynumber", dynlib: ws2dll, sideEffect.}
+
 proc socket*(af, typ, protocol: cint): SocketHandle {.
   stdcall, importc: "socket", dynlib: ws2dll.}