From f0f536dab34b7023e94f70e9ff7d4c5db1cb9e76 Mon Sep 17 00:00:00 2001
From: whd <7058128+superwhd@users.noreply.github.com>
Date: Tue, 1 Jun 2021 12:47:12 +0800
Subject: [PATCH] [udp] fix potential infinite loop in `Udp::GetEphemeralPort`
 (#6697)

The current implementation will go into an infinite loop when
mEphemeralPort == Tmf::kUdpPort, since rval is never updated in the
loop. This commit fixes this issue.
---
 src/core/net/udp6.cpp | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/src/core/net/udp6.cpp b/src/core/net/udp6.cpp
index b16f4bd46..74bebd4b2 100644
--- a/src/core/net/udp6.cpp
+++ b/src/core/net/udp6.cpp
@@ -407,8 +407,6 @@ exit:
 
 uint16_t Udp::GetEphemeralPort(void)
 {
-    uint16_t rval = mEphemeralPort;
-
     do
     {
         if (mEphemeralPort < kDynamicPortMax)
@@ -419,9 +417,9 @@ uint16_t Udp::GetEphemeralPort(void)
         {
             mEphemeralPort = kDynamicPortMin;
         }
-    } while (rval == Tmf::kUdpPort);
+    } while (mEphemeralPort == Tmf::kUdpPort);
 
-    return rval;
+    return mEphemeralPort;
 }
 
 Message *Udp::NewMessage(uint16_t aReserved, const Message::Settings &aSettings)