From 81d12fd14ae95ebe2ab9bc0935d307bda7cebd9e Mon Sep 17 00:00:00 2001
From: "J. Nick Koston" <nick@home-assistant.io>
Date: Tue, 10 Mar 2026 00:57:36 -1000
Subject: [PATCH] [socket] Hold lwip lock for entire write() operation
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Same pattern as writev — write() calls internal_write_() then
internal_output_(), each acquiring the lock separately. Hold
the lock at the outer scope so inner calls just bump the
recursion counter.
---
 esphome/components/socket/lwip_raw_tcp_impl.cpp | 1 +
 1 file changed, 1 insertion(+)

diff --git a/esphome/components/socket/lwip_raw_tcp_impl.cpp b/esphome/components/socket/lwip_raw_tcp_impl.cpp
index 0c0d64d198..d7fa6a2694 100644
--- a/esphome/components/socket/lwip_raw_tcp_impl.cpp
+++ b/esphome/components/socket/lwip_raw_tcp_impl.cpp
@@ -616,6 +616,7 @@ int LWIPRawImpl::internal_output_() {
 }
 
 ssize_t LWIPRawImpl::write(const void *buf, size_t len) {
+  LWIP_LOCK();  // Hold for write + optional output
   ssize_t written = this->internal_write_(buf, len);
   if (written == -1)
     return -1;