net: allow close() to ignore SSL failures due to disconnections (#15120)

* net: allow close() to ignore SSL failures due to disconnections

Comes with this PR is also a SIGPIPE handling contraption.

* net: don't do selectSigpipe() on macOS

macOS sockets have SO_NOSIGPIPE set, so an EPIPE doesn't necessary mean
that a SIGPIPE happened.

* net: fix alreadyBlocked logic

* net: WSAESHUTDOWN is also a disconnection error

tests/stdlib/tssl.nim

@@ -5,13 +5,16 @@ discard """
 import net, nativesockets
 
 when defined(posix): import os, posix
+else:
+  import winlean
+  const SD_SEND = 1
 
 when not defined(ssl):
   {.error: "This test must be compiled with -d:ssl".}
 
 const DummyData = "dummy data\n"
 
-proc connector(port: Port) {.thread.} =
+proc abruptShutdown(port: Port) {.thread.} =
   let clientContext = newContext(verifyMode = CVerifyNone)
   var client = newSocket(buffered = false)
   clientContext.wrapSocket(client)
@@ -20,11 +23,16 @@ proc connector(port: Port) {.thread.} =
   discard client.recvLine()
   client.getFd.close()
 
-proc main() =
-  let serverContext = newContext(verifyMode = CVerifyNone,
-                                 certFile = "tests/testdata/mycert.pem",
-                                 keyFile = "tests/testdata/mycert.pem")
+proc notifiedShutdown(port: Port) {.thread.} =
+  let clientContext = newContext(verifyMode = CVerifyNone)
+  var client = newSocket(buffered = false)
+  clientContext.wrapSocket(client)
+  client.connect("localhost", port)
 
+  discard client.recvLine()
+  client.close()
+
+proc main() =
   when defined(posix):
     var
       ignoreAction = SigAction(sa_handler: SIG_IGN)
@@ -34,7 +42,11 @@ proc main() =
     if sigaction(SIGPIPE, ignoreAction, oldSigPipeHandler) == -1:
       raiseOSError(osLastError(), "Couldn't ignore SIGPIPE")
 
-  block peer_close_without_shutdown:
+  let serverContext = newContext(verifyMode = CVerifyNone,
+                                 certFile = "tests/testdata/mycert.pem",
+                                 keyFile = "tests/testdata/mycert.pem")
+
+  block peer_close_during_write_without_shutdown:
     var server = newSocket(buffered = false)
     defer: server.close()
     serverContext.wrapSocket(server)
@@ -43,7 +55,7 @@ proc main() =
     server.listen()
 
     var clientThread: Thread[Port]
-    createThread(clientThread, connector, port)
+    createThread(clientThread, abruptShutdown, port)
 
     var peer: Socket
     try:
@@ -60,4 +72,63 @@ proc main() =
     finally:
       peer.close()
 
+  when defined(posix):
+    if sigaction(SIGPIPE, oldSigPipeHandler, nil) == -1:
+      raiseOSError(osLastError(), "Couldn't restore SIGPIPE handler")
+
+  block peer_close_before_received_shutdown:
+    var server = newSocket(buffered = false)
+    defer: server.close()
+    serverContext.wrapSocket(server)
+    server.bindAddr(address = "localhost")
+    let (_, port) = server.getLocalAddr()
+    server.listen()
+
+    var clientThread: Thread[Port]
+    createThread(clientThread, abruptShutdown, port)
+
+    var peer: Socket
+    try:
+      server.accept(peer)
+      peer.send(DummyData)
+
+      joinThread clientThread
+
+      # Tell the OS to close off the write side so shutdown attempts will
+      # be met with SIGPIPE.
+      when defined(posix):
+        discard peer.getFd.shutdown(SHUT_WR)
+      else:
+        discard peer.getFd.shutdown(SD_SEND)
+    finally:
+      peer.close()
+
+  block peer_close_after_received_shutdown:
+    var server = newSocket(buffered = false)
+    defer: server.close()
+    serverContext.wrapSocket(server)
+    server.bindAddr(address = "localhost")
+    let (_, port) = server.getLocalAddr()
+    server.listen()
+
+    var clientThread: Thread[Port]
+    createThread(clientThread, notifiedShutdown, port)
+
+    var peer: Socket
+    try:
+      server.accept(peer)
+      peer.send(DummyData)
+
+      doAssert peer.recv(1024) == "" # Get the shutdown notification
+      joinThread clientThread
+
+      # Tell the OS to close off the write side so shutdown attempts will
+      # be met with SIGPIPE.
+      when defined(posix):
+        discard peer.getFd.shutdown(SHUT_WR)
+      else:
+        discard peer.getFd.shutdown(SD_SEND)
+    finally:
+      peer.close()
+
 when isMainModule: main()