From 210b566437cfaf9b5ddeaebe8efddcf456285638 Mon Sep 17 00:00:00 2001
From: Christopher Dykes <cdykes@fb.com>
Date: Mon, 31 Oct 2016 11:59:37 -0700
Subject: [PATCH] In the portability implementation of sendmsg return a partial
 message send if it would block

Summary: If multiple iovs are passed to sendmsg, sendmsg is supposed to return the number of bytes sent if it would block, but only if the number of bytes sent is greater than 0.

Reviewed By: yfeldblum

Differential Revision: D4099691

fbshipit-source-id: e58fa71604966129b1fbd418c24b1bf012060428
---
 folly/portability/Sockets.cpp | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/folly/portability/Sockets.cpp b/folly/portability/Sockets.cpp
index 14f31fd0..5af38750 100755
--- a/folly/portability/Sockets.cpp
+++ b/folly/portability/Sockets.cpp
@@ -338,6 +338,10 @@ ssize_t sendmsg(int s, const struct msghdr* message, int fl) {
           message->msg_flags);
     }
     if (r == -1 || r != message->msg_iov[i].iov_len) {
+      errno = translate_wsa_error(WSAGetLastError());
+      if (WSAGetLastError() == WSAEWOULDBLOCK && bytesSent > 0) {
+        return bytesSent;
+      }
       return -1;
     }
     bytesSent += r;
-- 
2.34.1