MPPP: Another way to discard lost fragments

[l2tpns.git] / ppp.c

diff --git a/ppp.c b/ppp.c
index 4114bb4..036292a 100644 (file)
--- a/ppp.c
+++ b/ppp.c
@@ -1999,16 +1999,54 @@ 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)
-       {
-               this_fragmentation->fragment[begin_index].flags = 0;
-               this_fragmentation->fragment[begin_index].length = 0;
-               begin_index = (begin_index + 1) & MAXFRAGNUM_MASK;
+
+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)
+       {
+               // look for end of previous frame
+               // start at M-1, going backward
+               uint16_t index = M_index;
+               uint8_t end_or_hole_found = 0;
+
+               for (;;)
+               {
+                       fragmentt *this_frag;
+
+                       if (!end_or_hole_found)
+                       {
+                               fragmentt *front_frag = &this_fragmentation->frag[index];
+
+                               // before a MP_BEGIN, there must be a MP_END
+                               if (front_frag->length && (front_frag->flags & MP_BEGIN))
+                                       end_or_hole_found = 1;
+
+                               index = (index + (MAXFRAGNUM-1)) & MAXFRAGNUM_MASK;
+                               this_frag = &this_fragmentation->frag[index];
+
+                               // we are a hole or a MP_END
+                               if (!this_frag->length || (this_frag->flags & MP_END))
+                                       end_or_hole_found = 1;
+
+                               if (end_or_hole_found)
+                                       end_index = index;
+                       }
+
+                       if (end_or_hole_found)
+                       {
+                               this_frag->flags = 0;
+                               this_frag->length = 0;
+                       }
+
+                       if (index == this_fragmentation->start_index)
+                               break;
+               }
+
+               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);