X-Git-Url: http://git.sameswireless.fr/l2tpns.git/blobdiff_plain/e57abd6b9e216dee2a29897ba64d7fb24f5c6ecd..d674ec8153ca664525d38bab8c761cc34ecd79bd:/ppp.c

diff --git a/ppp.c b/ppp.c
index e21c103..3f5a9a5 100644
--- a/ppp.c
+++ b/ppp.c
@@ -1866,18 +1866,36 @@ void processmpin(sessionidt s, tunnelidt t, uint8_t *p, uint16_t l)
 	
 	// update M
 	sess_local[s].last_seq = seq_num;
-	if (seq_num < this_fragmentation->M)
-		this_fragmentation->M = seq_num;
-	else
 	{
-		uint32_t i, min = sess_local[(this_bundle->members[0])].last_seq;;
-		for (i = 1; i < this_bundle->num_of_links; i++)
+		/* seq # can be spread over the wrapping limit, and we must
+		   choose the "lowest" one, taking into account the wrapping:
+
+		   |-#-##--#----------------------M--###-#|
+
+		   but we must also care when the last highest seq # wraps,
+		   so we keep two minimums: one for the higher limit, and
+		   one for the lower one.
+
+		   In the nominal case, low_min = high_min.
+		*/
+		uint32_t i, low_min, high_min;
+		low_min = sess_local[(this_bundle->members[0])].last_seq;;
+		high_min = this_bundle->max_seq; // max_seq is impossible to reach
+
+		for (i = 0; i < this_bundle->num_of_links; i++)
 		{
 			uint32_t s_seq = sess_local[(this_bundle->members[i])].last_seq; 
-			if (s_seq < min)
-				min = s_seq;
+			if (s_seq < low_min)
+				low_min = s_seq;
+			if (s_seq >= this_fragmentation->M && s_seq < high_min)
+				high_min = s_seq;
 		}
-		this_fragmentation->M = min;
+
+		// if high_min was found, it's the "lowest" one
+		if (high_min < this_bundle->max_seq)
+			this_fragmentation->M = high_min;
+		else
+			this_fragmentation->M = low_min;
 	}
 
 	LOG(4, s, t, "MPPP: Setting M to %d\n", this_fragmentation->M);	
@@ -1981,16 +1999,55 @@ void processmpin(sessionidt s, tunnelidt t, uint8_t *p, uint16_t l)
 				break;
 		}
 	}
-	//discard fragments received before the recently assembled frame
-	begin_index = this_fragmentation->start_index;
-	this_fragmentation->start_index = (end_index + 1) & MAXFRAGNUM_MASK;
-	this_fragmentation->start_seq = (this_fragmentation->fragment[end_index].seq + 1) & (this_bundle->max_seq-1);
-	//clear length and flags of the discarded fragments
-	while (begin_index != this_fragmentation->start_index)
+
+discard_lost_frames:
+	//discard fragments numbererd below M and part of an unassembled frame,
+	//but not the one from the frame beginning just before M
+
+	// if we have something to discard
+	if (M_index != this_fragmentation->start_index)
 	{
-		this_fragmentation->fragment[begin_index].flags = 0;
-		this_fragmentation->fragment[begin_index].length = 0;
-		begin_index = (begin_index + 1) & MAXFRAGNUM_MASK;
+		uint8_t end_found = 0;
+		// look for end of previous frame
+		// start at M-1, going backward
+		for (end_index = (M_index + (MAXFRAGNUM-1)) & MAXFRAGNUM_MASK;
+		     end_index != this_fragmentation->start_index;
+		     end_index = (end_index + (MAXFRAGNUM-1)) & MAXFRAGNUM_MASK)
+		{
+			fragmentt *this_frag = &this_fragmentation->frag[end_index];
+			fragmentt *front_frag = &this_fragmentation->frag[(end_index+1)&MAXFRAGNUM_MASK];
+			// before a MP_BEGIN, we must be a MP_END
+			if (front_frag->length && (front_frag->flags & MP_BEGIN))
+			{
+				end_found = 1;
+				break;
+			}
+			// we are a MP_END
+			if (this_frag->length && (this_frag->flags & MP_END))
+			{
+				end_found = 1;
+				break;
+			}
+		}
+		// ok, we may not count it for found if end_index == this_fragmentation->start_index
+		// but it complicates things too much and it will be discarded on next round anyway
+
+		//clear length and flags of the discarded fragments
+		if (end_found)
+		{
+			begin_index = this_fragmentation->start_index;
+			while (begin_index != end_index)
+			{
+				this_fragmentation->fragment[begin_index].flags = 0;
+				this_fragmentation->fragment[begin_index].length = 0;
+				begin_index = (begin_index + 1) & MAXFRAGNUM_MASK;
+			}
+			this_fragmentation->fragment[begin_index].flags = 0;
+			this_fragmentation->fragment[begin_index].length = 0;
+
+			this_fragmentation->start_index = (end_index + 1) & MAXFRAGNUM_MASK;
+			this_fragmentation->start_seq = (this_fragmentation->fragment[end_index].seq + 1) & (this_bundle->max_seq-1);
+		}
 	}
 
 	LOG(4, s, t, "MPPP after assembling: M index is =%d, start index is = %d, start seq=%d\n",M_index, this_fragmentation->start_index, this_fragmentation->start_seq);