From 101bcba26fda95e166f0692ba5bbc120b647f40e Mon Sep 17 00:00:00 2001
From: Hanno Becker <hanno.becker@arm.com>
Date: Tue, 21 Aug 2018 16:39:51 +0100
Subject: [PATCH] UDP proxy: Allow more than one message to be delayed

Previously, the UDP proxy could only remember one delayed message
for future transmission; if two messages were delayed in succession,
without another one being normally forwarded in between,
the message that got delayed first would be dropped.

This commit enhances the UDP proxy to allow to delay an arbitrary
(compile-time fixed) number of messages in succession.
---
 programs/test/udp_proxy.c | 45 ++++++++++++++++++++++++++++-----------
 1 file changed, 33 insertions(+), 12 deletions(-)

diff --git a/programs/test/udp_proxy.c b/programs/test/udp_proxy.c
index 77eaa5d2f..0428d2888 100644
--- a/programs/test/udp_proxy.c
+++ b/programs/test/udp_proxy.c
@@ -556,11 +556,37 @@ int send_packet( const packet *p, const char *why )
     return( 0 );
 }
 
-static packet prev;
+#define MAX_DELAYED_MSG 5
+static size_t prev_len;
+static packet prev[MAX_DELAYED_MSG];
 
 void clear_pending( void )
 {
     memset( &prev, 0, sizeof( packet ) );
+    prev_len = 0;
+}
+
+void delay_packet( packet *delay )
+{
+    if( prev_len == MAX_DELAYED_MSG )
+        return;
+
+    memcpy( &prev[prev_len++], delay, sizeof( packet ) );
+}
+
+int send_delayed()
+{
+    uint8_t offset;
+    int ret;
+    for( offset = 0; offset < prev_len; offset++ )
+    {
+        ret = send_packet( &prev[offset], "delayed" );
+        if( ret != 0 )
+            return( ret );
+    }
+
+    clear_pending();
+    return( 0 );
 }
 
 /*
@@ -647,7 +673,7 @@ int handle_message( const char *way,
         if( strcmp( delay_list[ delay_idx ], cur.type ) == 0 )
         {
             /* Delay message */
-            memcpy( &prev, &cur, sizeof( packet ) );
+            delay_packet( &cur );
 
             /* Remove entry from list */
             mbedtls_free( delay_list[delay_idx] );
@@ -676,12 +702,11 @@ int handle_message( const char *way,
                strcmp( cur.type, "ApplicationData" ) != 0 &&
                ! ( opt.protect_hvr &&
                    strcmp( cur.type, "HelloVerifyRequest" ) == 0 ) &&
-               prev.dst == NULL &&
                cur.len != (size_t) opt.protect_len &&
                dropped[id] < DROP_MAX &&
                rand() % opt.delay == 0 ) )
     {
-        memcpy( &prev, &cur, sizeof( packet ) );
+        delay_packet( &cur );
     }
     else
     {
@@ -689,14 +714,10 @@ int handle_message( const char *way,
         if( ( ret = send_packet( &cur, "forwarded" ) ) != 0 )
             return( ret );
 
-        /* send previously delayed message if any */
-        if( prev.dst != NULL )
-        {
-            ret = send_packet( &prev, "delayed" );
-            memset( &prev, 0, sizeof( packet ) );
-            if( ret != 0 )
-                return( ret );
-        }
+        /* send previously delayed messages if any */
+        ret = send_delayed();
+        if( ret != 0 )
+            return( ret );
     }
 
     return( 0 );