From 96fa1cd4a8f17e48fa0ee7bd1a0ec851d6945e6f Mon Sep 17 00:00:00 2001
From: Aman Sharma <amsharma@meta.com>
Date: Wed, 29 Jan 2025 13:10:57 -0800
Subject: [PATCH] Make a writem API with just iovecs [5/n]

Summary:
**Background for the diff stack**: We'd like to excise the usage of folly from a library that we maintain (quic), which is why we'd like to have a version of `writemGSO` that takes in iovecs instead of IOBufs.

**What this diff is doing**: We're creating a new `writemv` function that does basically the same thing that `writem` does, except it uses `iovec`s instead of `IOBuf`s. This is pretty similar to `writem`.

Reviewed By: mjoras

Differential Revision: D68736205

fbshipit-source-id: b6dc9b1740d31bff97ec9e0b49923717f0b819b5
---
 folly/io/async/AsyncUDPSocket.cpp |  8 ++++++++
 folly/io/async/AsyncUDPSocket.h   | 13 +++++++++++++
 2 files changed, 21 insertions(+)

diff --git a/folly/io/async/AsyncUDPSocket.cpp b/folly/io/async/AsyncUDPSocket.cpp
index ea06074adfd..1ae5a8968b5 100644
--- a/folly/io/async/AsyncUDPSocket.cpp
+++ b/folly/io/async/AsyncUDPSocket.cpp
@@ -865,6 +865,14 @@ int AsyncUDPSocket::writemGSO(
   return ret;
 }
 
+int AsyncUDPSocket::writemv(
+    Range<SocketAddress const*> addrs,
+    iovec* iov,
+    size_t* numIovecsInBuffer,
+    size_t count) {
+  return writemGSOv(addrs, iov, numIovecsInBuffer, count, nullptr);
+}
+
 int AsyncUDPSocket::writemGSOv(
     Range<SocketAddress const*> addrs,
     iovec* iov,
diff --git a/folly/io/async/AsyncUDPSocket.h b/folly/io/async/AsyncUDPSocket.h
index cc5e34daf96..e6910490a86 100644
--- a/folly/io/async/AsyncUDPSocket.h
+++ b/folly/io/async/AsyncUDPSocket.h
@@ -270,6 +270,19 @@ class AsyncUDPSocket : public EventHandler {
       const std::unique_ptr<folly::IOBuf>* bufs,
       size_t count);
 
+  /**
+   * Send the data in buffers to destination. Returns the return code from
+   * ::sendmmsg.
+   * iov is an array of iovecs, which is composed of "count" messages that
+   * need to be sent. Each message can have multiple iovecs. The number of
+   * iovecs per message is specified in numIovecsInBuffer.
+   */
+  virtual int writemv(
+      Range<SocketAddress const*> addrs,
+      iovec* iov,
+      size_t* numIovecsInBuffer,
+      size_t count);
+
   /**
    * Send the data in buffer to destination. Returns the return code from
    * ::sendmsg.