[vlc-devel] [PATCH 1/2] amt: refactor to account for packet size

[Alexandre Janniaux]

+ remove signed/unsigned implicit conversion from recv on Windows
+ ensure usage of size_t where needed
+ ensure packet size is no more than what was read
+ ensure zero-sized datagrams are removed too
---
 modules/access/amt.c | 26 ++++++++++++++------------
 1 file changed, 14 insertions(+), 12 deletions(-)

diff --git a/modules/access/amt.c b/modules/access/amt.c
index 7706bfd573..b5ed878ce8 100644
--- a/modules/access/amt.c
+++ b/modules/access/amt.c
@@ -553,7 +553,7 @@ static int Control( stream_t *p_access, int i_query, va_list args )
 static block_t *BlockAMT(stream_t *p_access, bool *restrict eof)
 {
     access_sys_t *sys = p_access->p_sys;
-    ssize_t len = 0, shift = 0, tunnel = IP_HDR_LEN + UDP_HDR_LEN + AMT_HDR_LEN;
+    size_t tunnel = IP_HDR_LEN + UDP_HDR_LEN + AMT_HDR_LEN;
 
     /* Allocate anticipated MTU buffer for holding the UDP packet suitable for native or AMT tunneled multicast */
     block_t *pkt = block_Alloc( sys->mtu + tunnel );
@@ -591,17 +591,17 @@ static block_t *BlockAMT(stream_t *p_access, bool *restrict eof)
     if( sys->tryAMT )
     {
         /* AMT is a wrapper for UDP streams, so recv is used. */
-        len = recv( sys->sAMT, pkt->p_buffer, sys->mtu + tunnel, 0 );
+        ssize_t len = vlc_recv_i11e( sys->sAMT, pkt->p_buffer, sys->mtu + tunnel, 0 );
 
         /* Check for the integrity of the received AMT packet */
-        if( len < 0 || *(pkt->p_buffer) != AMT_MULT_DATA )
+        if( len <= 0 || *(pkt->p_buffer) != AMT_MULT_DATA )
             goto error;
 
-        /* Set the offet to the first byte of the payload */
-        shift += tunnel;
+        /* Ensure packet size is no more than what was read */
+        pkt->i_buffer = (size_t)len;
 
         /* If the length received is less than the AMT tunnel header then it's truncated */
-        if( len < tunnel )
+        if( pkt->i_buffer < tunnel )
         {
             msg_Err(p_access, "%zd bytes packet truncated (MTU was %zd)", len, sys->mtu);
             pkt->i_flags |= BLOCK_FLAG_CORRUPTED;
@@ -610,7 +610,9 @@ static block_t *BlockAMT(stream_t *p_access, bool *restrict eof)
         /* Otherwise subtract the length of the AMT encapsulation from the packet received */
         else
         {
-            len -= tunnel;
+            /* Set the offset to payload start */
+            pkt->p_buffer += tunnel;
+            pkt->i_buffer -= tunnel;
         }
     }
     /* Otherwise pull native multicast */
@@ -618,12 +620,12 @@ static block_t *BlockAMT(stream_t *p_access, bool *restrict eof)
     {
         struct sockaddr temp;
         socklen_t temp_size = sizeof( struct sockaddr );
-        len = recvfrom( sys->sAMT, (char *)pkt->p_buffer, sys->mtu + tunnel, 0, (struct sockaddr*)&temp, &temp_size );
-    }
+        ssize_t len = vlc_recvfrom_i11e( sys->sAMT, pkt->p_buffer, sys->mtu + tunnel, 0, (struct sockaddr*)&temp, &temp_size );
+        if( len < 0 )
+            goto error;
 
-    /* Set the offset to payload start */
-    pkt->p_buffer += shift;
-    pkt->i_buffer -= shift;
+        pkt->i_buffer = (size_t)len;
+    }
 
     return pkt;
 
-- 
2.26.0