remove oldest pcbs in time-wait state when max number of them is reached (#17)

Author: d-a-v

glue-lwip/arduino/lwipopts.h

@@ -2992,6 +2992,7 @@
 
 /*
    --------------------------------------------------
+   ------------- End of original lwipopts -----------
    --------------------------------------------------
 */
 
@@ -3008,4 +3009,34 @@ struct netif;
 #endif
 LWIP_ERR_T lwip_unhandled_packet (struct pbuf* pbuf, struct netif* netif) __attribute__((weak));
 
+/*
+   --------------------------------------------------
+   ----------------- TIME-WAIT tweak ----------------
+   --------------------------------------------------
+   port @me-no-dev time-wait tweak
+   https://github.com/esp8266/Arduino/commit/07f4d4c241df2c552899857f39a4295164f686f2#diff-f8258e71e25fb9985ca3799e3d8b88ecR399
+*/
+
+void tcp_kill_timewait (void);
+#define TCP_TW_LIMIT(l)                \
+  if (l) do {                          \
+    u32_t count_plus_1 = 1;            \
+    struct tcp_pcb* tmp = tcp_tw_pcbs; \
+    if (tmp)                           \
+      while ((tmp = tmp->next))        \
+        ++count_plus_1;                \
+    while (--count_plus_1 > (l))       \
+      /* kill the oldest */            \
+      /* pcb in TW state */            \
+      tcp_kill_timewait();             \
+  } while (0)
+
+/**
+ * MEMP_NUM_TCP_PCB_TIME_WAIT: the number of TCP pcbs in TIME_WAIT state.
+ * (requires the LWIP_TCP option, 0 = disabled)
+ */
+#ifndef MEMP_NUM_TCP_PCB_TIME_WAIT
+#define MEMP_NUM_TCP_PCB_TIME_WAIT       5
+#endif
+
 #endif // MYLWIPOPTS_H

makefiles/Makefile.lwip2

@@ -14,7 +14,13 @@ OBJ = \
 BUILD_INCLUDES = -I$(BUILD) -I$(SDK)/include -Iinclude -I../../glue -I../../glue-lwip -I../../glue-lwip/$(target)
 #BUILD_INCLUDES += -I../../lwip2-contrib-src/apps/ping
 
-all: $(LWIP_LIB)
+all: patches $(LWIP_LIB)
+
+patches: .patched
+
+.patched:
+	patch -d .. -p1 < ../../patches/time-wait.patch
+	touch .patched
 
 include ../../makefiles/Makefile.defs
 include ../../makefiles/Makefile.rules

patches/time-wait.patch

@@ -0,0 +1,49 @@
+diff --git a/src/core/tcp.c b/src/core/tcp.c
+index b5144d2..1dfe573 100644
+--- a/src/core/tcp.c
++++ b/src/core/tcp.c
+@@ -281,6 +281,7 @@ tcp_close_shutdown(struct tcp_pcb *pcb, u8_t rst_on_unacked_data)
+         /* move to TIME_WAIT since we close actively */
+         pcb->state = TIME_WAIT;
+         TCP_REG(&tcp_tw_pcbs, pcb);
++        TCP_TW_LIMIT(MEMP_NUM_TCP_PCB_TIME_WAIT);
+       } else {
+         /* CLOSE_WAIT: deallocate the pcb since we already sent a RST for it */
+         if (tcp_input_pcb == pcb) {
+@@ -1523,7 +1524,7 @@ tcp_kill_state(enum tcp_state state)
+  * Kills the oldest connection that is in TIME_WAIT state.
+  * Called from tcp_alloc() if no more connections are available.
+  */
+-static void
++void
+ tcp_kill_timewait(void)
+ {
+   struct tcp_pcb *pcb, *inactive;
+diff --git a/src/core/tcp_in.c b/src/core/tcp_in.c
+index 5e839ff..41c7d43 100644
+--- a/src/core/tcp_in.c
++++ b/src/core/tcp_in.c
+@@ -916,6 +916,7 @@ tcp_process(struct tcp_pcb *pcb)
+         TCP_RMV_ACTIVE(pcb);
+         pcb->state = TIME_WAIT;
+         TCP_REG(&tcp_tw_pcbs, pcb);
++        TCP_TW_LIMIT(MEMP_NUM_TCP_PCB_TIME_WAIT);
+       } else {
+         tcp_ack_now(pcb);
+         pcb->state = CLOSING;
+@@ -934,6 +935,7 @@ tcp_process(struct tcp_pcb *pcb)
+       TCP_RMV_ACTIVE(pcb);
+       pcb->state = TIME_WAIT;
+       TCP_REG(&tcp_tw_pcbs, pcb);
++      TCP_TW_LIMIT(MEMP_NUM_TCP_PCB_TIME_WAIT);
+     }
+     break;
+   case CLOSING:
+@@ -944,6 +946,7 @@ tcp_process(struct tcp_pcb *pcb)
+       TCP_RMV_ACTIVE(pcb);
+       pcb->state = TIME_WAIT;
+       TCP_REG(&tcp_tw_pcbs, pcb);
++      TCP_TW_LIMIT(MEMP_NUM_TCP_PCB_TIME_WAIT);
+     }
+     break;
+   case LAST_ACK: