cmd/docker-proxy: set O_NONBLOCK unconditionally

Prior to commit b5bf89c, all socket fds passed to the docker-proxy
were getting the O_NONBLOCK flag set. However, that commit added support
for SCTP socket-passing, and had to conditionally guard this behavior to
not use it on SCTP sockets due to ishidawataru/sctp not clearing the
flag.

A fix was made in ishidawataru/sctp (see [1]), so we can remove that
condition.

[1]: ishidawataru/sctp@4b890084db30

Signed-off-by: Albin Kerouanton <albinker@gmail.com>

Author: akerouanton

cmd/docker-proxy/main_linux.go

@@ -178,11 +178,7 @@ func parseFlags() ProxyConfig {
 	}
 
 	if useListenFd {
-		// Unlike the stdlib, passing a non-blocking socket to `sctp.FileListener`
-		// will result in a non-blocking Accept(). So, do not set this flag for SCTP.
-		if config.Proto != "sctp" {
-			_ = syscall.SetNonblock(int(listenSockFd), true)
-		}
+		_ = syscall.SetNonblock(int(listenSockFd), true)
 		config.ListenSock = os.NewFile(listenSockFd, "listen-sock")
 	}