internal/socket: check for EWOULDBLOCK on all platforms

Don't make the check for EWOULDBLOCK zos-specific. Most platforms define
EAGAIN and EWOULDBLOCK with the same underlying value. Thus, the
additional check will be a no-op on them. On platforms where EAGAIN and
EWOULDBLOCK have different underlying values, we probably want to check
both as well.

As pointed out by Michael Munday in CL 264028.

Change-Id: Id3404fc4440c66a3484975b4c94b4ebb788b80a1
Reviewed-on: https://go-review.googlesource.com/c/net/+/295569
Trust: Tobias Klauser <[email protected]>
Run-TryBot: Tobias Klauser <[email protected]>
Reviewed-by: Ian Lance Taylor <[email protected]>

Author: tklauser

internal/socket/rawconn_msg.go

@@ -9,7 +9,6 @@ package socket
 
 import (
 	"os"
-	"runtime"
 	"syscall"
 )
 
@@ -26,7 +25,7 @@ func (c *Conn) recvMsg(m *Message, flags int) error {
 	var n int
 	fn := func(s uintptr) bool {
 		n, operr = recvmsg(s, &h, flags)
-		if operr == syscall.EAGAIN || (runtime.GOOS == "zos" && operr == syscall.EWOULDBLOCK) {
+		if operr == syscall.EAGAIN || operr == syscall.EWOULDBLOCK {
 			return false
 		}
 		return true
@@ -63,7 +62,7 @@ func (c *Conn) sendMsg(m *Message, flags int) error {
 	var n int
 	fn := func(s uintptr) bool {
 		n, operr = sendmsg(s, &h, flags)
-		if operr == syscall.EAGAIN || (runtime.GOOS == "zos" && operr == syscall.EWOULDBLOCK) {
+		if operr == syscall.EAGAIN || operr == syscall.EWOULDBLOCK {
 			return false
 		}
 		return true