lwip_tcp: детект и защита от self-loop (pcb->next==pcb) в tw_pcbs

tcp_slowtmr: после tcp_free проверка pcb==pcb2 → ctx->tw_pcbs=NULL, break
tcp_kill_timewait: проверка inactive->next==inactive → ctx->tw_pcbs=NULL, tcp_free
lwip_tcp_input: проверка pcb->next==pcb перед tcp_timewait_input → tcp_abort
все 3 лога выводят next_owner для диагностики источника self-ссылки

src/lwip_tcp/lwip_tcp.c

@@ -812,7 +812,15 @@ void tcp_slowtmr(struct lwip_tcp_ctx *ctx)
             }
             pcb2 = pcb;
             pcb = pcb->next;
+            int self_loop = (pcb == pcb2);
+            uint8_t sl_owner = pcb2->next_owner;
             tcp_free(pcb2);
+            if (self_loop) {
+                DEBUG_ERROR(DEBUG_CATEGORY_ALL, "TW_PCBS SELF-LOOP in tcp_slowtmr: freed pcb=%p state=TIME_WAIT port=%u next_owner=%d, clearing tw_pcbs",
+                            (void*)pcb2, pcb2->local_port, sl_owner);
+                ctx->tw_pcbs = NULL;
+                break;
+            }
         } else {
             prev = pcb;
             pcb = pcb->next;
@@ -1036,7 +1044,16 @@ static void tcp_kill_timewait(struct lwip_tcp_ctx *ctx)
             inactive = pcb;
         }
     }
-    if (inactive != NULL) tcp_abort(inactive);
+    if (inactive != NULL) {
+        if (inactive->next == inactive) {
+            DEBUG_ERROR(DEBUG_CATEGORY_ALL, "TW_PCBS SELF-LOOP in tcp_kill_timewait: aborting pcb=%p next_owner=%d, clearing tw_pcbs",
+                        (void*)inactive, inactive->next_owner);
+            ctx->tw_pcbs = NULL;
+            tcp_free(inactive);
+        } else {
+            tcp_abort(inactive);
+        }
+    }
 }
 
 static void tcp_handle_closepend(struct lwip_tcp_ctx *ctx)

src/lwip_tcp/lwip_tcp_in.c

@@ -221,7 +221,13 @@ void lwip_tcp_input(struct lwip_tcp_ctx *ctx, struct pbuf *p,
                 pcb->local_port  == dport &&
                 pcb->remote_ip   == src_ip &&
                 pcb->local_ip    == dst_ip) {
-                tcp_timewait_input(pcb);
+                if (pcb->next == pcb) {
+                    DEBUG_ERROR(DEBUG_CATEGORY_ALL, "TW_PCBS SELF-LOOP in lwip_tcp_input: pcb=%p sport=%u dport=%u next_owner=%d, aborting",
+                                (void*)pcb, sport, dport, pcb->next_owner);
+                    tcp_abort(pcb);
+                } else {
+                    tcp_timewait_input(pcb);
+                }
                 pbuf_free(p);
                 return;
             }