diff --git a/src/lwip_tcp/lwip_tcp.c b/src/lwip_tcp/lwip_tcp.c
index e5583b03..8f9bbca0 100644
--- a/src/lwip_tcp/lwip_tcp.c
+++ b/src/lwip_tcp/lwip_tcp.c
@@ -749,6 +749,7 @@ void tcp_slowtmr(struct lwip_tcp_ctx *ctx)
             tcp_pcb_purge(pcb);
             if (prev != NULL) {
                 prev->next = pcb->next;
+                prev->next_owner = PCB_NEXT_SLOWTMR;
             } else {
                 ctx->active_pcbs = pcb->next;
             }
@@ -787,7 +788,13 @@ void tcp_slowtmr(struct lwip_tcp_ctx *ctx)
     // ---- process TIME-WAIT PCBs ----
     prev = NULL;
     pcb = ctx->tw_pcbs;
+    int tw_iter = 0;
     while (pcb != NULL) {
+        if (++tw_iter > TCP_TW_MAX) {
+            DEBUG_ERROR(DEBUG_CATEGORY_ALL, "TW_PCBS LOOP in tcp_slowtmr: %d iterations, aborting pcb=%p state=%d port=%u next_owner=%d", tw_iter, (void*)pcb, pcb->state, pcb->local_port, pcb->next_owner);
+            tcp_abort(pcb);
+            break;
+        }
         pcb_remove = 0;
 
         if ((uint32_t)(ctx->ticks - pcb->tmr) > 2 * TCP_MSL / TCP_SLOW_INTERVAL) {
@@ -799,6 +806,7 @@ void tcp_slowtmr(struct lwip_tcp_ctx *ctx)
             tcp_pcb_purge(pcb);
             if (prev != NULL) {
                 prev->next = pcb->next;
+                prev->next_owner = PCB_NEXT_SLOWTMR;
             } else {
                 ctx->tw_pcbs = pcb->next;
             }
@@ -1016,7 +1024,13 @@ static void tcp_kill_timewait(struct lwip_tcp_ctx *ctx)
     if (!ctx) return;
     inactivity = 0;
     inactive = NULL;
+    int tw_iter = 0;
     for (pcb = ctx->tw_pcbs; pcb != NULL; pcb = pcb->next) {
+        if (++tw_iter > TCP_TW_MAX) {
+            DEBUG_ERROR(DEBUG_CATEGORY_ALL, "TW_PCBS LOOP in tcp_kill_timewait: %d iterations, aborting pcb=%p state=%d port=%u next_owner=%d", tw_iter, (void*)pcb, pcb->state, pcb->local_port, pcb->next_owner);
+            tcp_abort(pcb);
+            return;
+        }
         if ((uint32_t)(ctx->ticks - pcb->tmr) >= inactivity) {
             inactivity = ctx->ticks - pcb->tmr;
             inactive = pcb;
@@ -1080,8 +1094,8 @@ struct tcp_pcb *tcp_alloc(struct lwip_tcp_ctx *ctx, uint8_t prio)
         pcb->rcv_wnd = pcb->rcv_ann_wnd = TCPWND16(TCP_WND);
         pcb->ttl = 64;
         pcb->mss = INITIAL_MSS;
-        pcb->rto = 3000 / TCP_SLOW_INTERVAL;
-        pcb->sv = 3000 / TCP_SLOW_INTERVAL;
+        pcb->rto = (int16_t)(ctx->rto_min_ms / TCP_SLOW_INTERVAL);
+        pcb->sv  = (int16_t)(ctx->rto_min_ms / TCP_SLOW_INTERVAL);
         pcb->rtime = -1;
         pcb->cwnd = 1;
         DEBUG_INFO(DEBUG_CATEGORY_GENERAL, "tcp_alloc: cwnd=%u snd_buf=%u mss=%u snd_wnd=%u", pcb->cwnd, pcb->snd_buf, pcb->mss, pcb->snd_wnd);
diff --git a/src/lwip_tcp/lwip_tcp.h b/src/lwip_tcp/lwip_tcp.h
index 9300d549..0fa4ccae 100644
--- a/src/lwip_tcp/lwip_tcp.h
+++ b/src/lwip_tcp/lwip_tcp.h
@@ -67,6 +67,15 @@ enum tcp_err_enum {
     LERR_CLSD       = -15,
     LERR_ARG        = -16
 };
+
+// кто последним записал pcb->next (диагностика зацикливания tw_pcbs)
+enum pcb_next_owner {
+    PCB_NEXT_NONE     = 0,
+    PCB_NEXT_REG      = 1,
+    PCB_NEXT_RMV      = 2,
+    PCB_NEXT_SLOWTMR  = 3,
+    PCB_NEXT_INPUT    = 4,
+};
 typedef int err_t;
 
 // Forward declaration for callbacks
@@ -167,6 +176,8 @@ struct tcp_pcb {
     tcp_poll_fn poll;
     tcp_err_fn errf;
 
+    uint8_t next_owner;     // who last wrote pcb->next (enum pcb_next_owner)
+
     uint32_t keep_idle;
     uint8_t persist_cnt;
     uint8_t persist_backoff;
@@ -182,6 +193,7 @@ struct tcp_pcb_listen {
     uint8_t prio;
     uint16_t local_port;
     uint32_t local_ip;
+    uint8_t next_owner;
     tcp_accept_fn accept;
 };
 
diff --git a/src/lwip_tcp/lwip_tcp_in.c b/src/lwip_tcp/lwip_tcp_in.c
index 88bb446d..044254b9 100644
--- a/src/lwip_tcp/lwip_tcp_in.c
+++ b/src/lwip_tcp/lwip_tcp_in.c
@@ -198,7 +198,9 @@ void lwip_tcp_input(struct lwip_tcp_ctx *ctx, struct pbuf *p,
             pcb->local_ip    == dst_ip) {
             if (prev != NULL) {
                 prev->next = pcb->next;
+                prev->next_owner = PCB_NEXT_INPUT;
                 pcb->next = ctx->active_pcbs;
+                pcb->next_owner = PCB_NEXT_INPUT;
                 ctx->active_pcbs = pcb;
             }
             break;
@@ -207,7 +209,14 @@ void lwip_tcp_input(struct lwip_tcp_ctx *ctx, struct pbuf *p,
     }
 
     if (pcb == NULL) {
+        int tw_iter = 0;
         for (pcb = ctx->tw_pcbs; pcb != NULL; pcb = pcb->next) {
+            if (++tw_iter > TCP_TW_MAX) {
+                DEBUG_ERROR(DEBUG_CATEGORY_ALL, "TW_PCBS LOOP in lwip_tcp_input: %d iterations, aborting pcb=%p sport=%u dport=%u next_owner=%d", tw_iter, (void*)pcb, sport, dport, pcb->next_owner);
+                tcp_abort(pcb);
+                pbuf_free(p);
+                return;
+            }
             if (pcb->remote_port == sport &&
                 pcb->local_port  == dport &&
                 pcb->remote_ip   == src_ip &&
@@ -231,7 +240,9 @@ void lwip_tcp_input(struct lwip_tcp_ctx *ctx, struct pbuf *p,
         if (lpcb != NULL) {
             if (prev != NULL) {
                 ((struct tcp_pcb_listen *)prev)->next = lpcb->next;
+                ((struct tcp_pcb_listen *)prev)->next_owner = PCB_NEXT_INPUT;
                 lpcb->next = ctx->listen_pcbs;
+                lpcb->next_owner = PCB_NEXT_INPUT;
                 ctx->listen_pcbs = (struct tcp_pcb *)lpcb;
             }
             tcp_listen_input(lpcb);
diff --git a/src/lwip_tcp/lwip_tcp_opts.h b/src/lwip_tcp/lwip_tcp_opts.h
index 2057072b..37d972fe 100644
--- a/src/lwip_tcp/lwip_tcp_opts.h
+++ b/src/lwip_tcp/lwip_tcp_opts.h
@@ -14,15 +14,17 @@
 #define TCP_FAST_INTERVAL      TCP_TMR_INTERVAL
 #define TCP_SLOW_INTERVAL      (2 * TCP_TMR_INTERVAL)
 
-#define TCP_FIN_WAIT_TIMEOUT   20000     // ms
-#define TCP_SYN_RCVD_TIMEOUT   20000     // ms
-#define TCP_MSL                60000     // ms
+#define TCP_FIN_WAIT_TIMEOUT   6000      // ms
+#define TCP_SYN_RCVD_TIMEOUT   6000      // ms
+#define TCP_MSL                25000     // ms (2*MSL = 50s)
 #define TCP_OOSEQ_TIMEOUT      6         // x RTO
 
 #define TCP_KEEPIDLE_DEFAULT   7200000   // ms (unused, no keepalive)
 #define TCP_KEEPINTVL_DEFAULT  75000
 #define TCP_KEEPCNT_DEFAULT    9
 
+#define TCP_TW_MAX             256       // max tw_pcbs before cycle detection triggers
+
 #define TCP_WND_SCALE          0         // disabled
 #define TCP_TIMESTAMPS         0         // disabled
 #define TCP_SACK_OUT           0         // disabled
diff --git a/src/lwip_tcp/lwip_tcp_priv.h b/src/lwip_tcp/lwip_tcp_priv.h
index eafcb3c1..482727a0 100644
--- a/src/lwip_tcp/lwip_tcp_priv.h
+++ b/src/lwip_tcp/lwip_tcp_priv.h
@@ -3,6 +3,7 @@
 #define LWIP_TCP_PRIV_H
 
 #include "lwip_tcp.h"
+#include "lwip_tcp_opts.h"
 #include <string.h>
 
 // Packed struct support
@@ -235,13 +236,15 @@ void lwip_tcp_stats_clear(struct lwip_tcp_ctx *ctx);
 
 // PCB list management
 #define TCP_REG(pcbs, npcb) do { \
+    (npcb)->next_owner = PCB_NEXT_REG; \
     (npcb)->next = *(pcbs); *(pcbs) = (npcb); \
 } while(0)
 
 #define TCP_RMV(pcbs, npcb) do { \
     if(*(pcbs) == (npcb)) { *(pcbs) = (*pcbs)->next; } \
-    else { struct tcp_pcb *tmp; for(tmp = *(pcbs); tmp != NULL; tmp = tmp->next) { if(tmp->next == (npcb)) { tmp->next = (npcb)->next; break; } } } \
+    else { struct tcp_pcb *_tmp; int _rmv_i = 0; for(_tmp = *(pcbs); _tmp != NULL && _rmv_i < TCP_TW_MAX; _tmp = _tmp->next) { if(++_rmv_i >= TCP_TW_MAX) break; if(_tmp->next == (npcb)) { _tmp->next_owner = PCB_NEXT_SLOWTMR; _tmp->next = (npcb)->next; break; } } } \
     (npcb)->next = NULL; \
+    (npcb)->next_owner = PCB_NEXT_RMV; \
 } while(0)
 
 #define TCP_REG_ACTIVE(ctx, npcb) TCP_REG(&(ctx)->active_pcbs, npcb)
diff --git a/src/proxy/tcp_proxy_client.c b/src/proxy/tcp_proxy_client.c
index 9501f069..7f167b10 100644
--- a/src/proxy/tcp_proxy_client.c
+++ b/src/proxy/tcp_proxy_client.c
@@ -496,7 +496,7 @@ static void tcp_proxy_client_handle_error(struct tcp_proxy_client* p, uint32_t s
 static void tcp_proxy_client_handle_fin(struct tcp_proxy_client* p, uint32_t stream_id) {
     struct tcp_proxy_client_conn* pc = tcp_proxy_client_find_conn(p, stream_id);
     if (!pc || !pc->pcb) return;
-    DEBUG_INFO(DEBUG_CATEGORY_SOCKET, "PROXY FIN FROM exit sid=%08x — shutdown write (send FIN to local)", stream_id);
+    DEBUG_INFO(DEBUG_CATEGORY_SOCKET, "PROXY FIN FROM exit sid=%08x pcb_state=%u — shutdown write (send FIN to local)", stream_id, pc->pcb->state);
     pc->fin_remote = 1;
     if (pc->pcb->state != TIME_WAIT && pc->pcb->state != CLOSED)
         tcp_shutdown(pc->pcb, 0, 1);