From bfba1352e44d462a8acb2a45fc11f7f88f4943c6 Mon Sep 17 00:00:00 2001
From: dmiller <dmiller@e0a8ed71-7df4-0310-8962-fdc924857419>
Date: Thu, 7 Nov 2024 23:43:26 +0000
Subject: [PATCH] Fix UDP listen on Windows: recvfrom behaves differently.

---
 ncat/ncat_listen.c | 20 ++++++++++++++++++--
 1 file changed, 18 insertions(+), 2 deletions(-)

diff --git a/ncat/ncat_listen.c b/ncat/ncat_listen.c
index 7757a9c65..954137ab6 100644
--- a/ncat/ncat_listen.c
+++ b/ncat/ncat_listen.c
@@ -450,8 +450,24 @@ static void handle_connection(int socket_accept, int type, fd_set *listen_fds)
       int nbytes = recvfrom(socket_accept, buf, sizeof(buf), MSG_PEEK,
           &s.remoteaddr.sockaddr, &s.ss_len);
       if (nbytes < 0) {
-        loguser("%s.\n", socket_strerror(socket_errno()));
-        return;
+          int err = socket_errno();
+          switch (err) {
+              // Recoverable try-again errors:
+              case EINTR:
+              case EAGAIN:
+                  loguser("%s.\n", socket_strerror(socket_errno()));
+                  return;
+              // Ignorable errors:
+              // Windows returns SOCKET_ERROR and WSAEMSGSIZE instead of truncating!
+              case EMSGSIZE:
+                  if (s.remoteaddr.sockaddr.sa_family != AF_UNSPEC)
+                      break;
+              // everything else:
+              default:
+                  die("recvfrom");
+                  return;
+                  break;
+          }
       }
       /*
        * We're using connected udp. This has the down side of only