From d64f04bc95845d7de3d8cfbfe885ead1b80f10da Mon Sep 17 00:00:00 2001
From: Chen Wen <chenwen@espressif.com>
Date: Wed, 24 Jul 2019 13:26:38 +0800
Subject: [PATCH] feat(dhcp): add menuconfig for DHCP discover retransmission
 interval

---
 components/lwip/Kconfig                         | 7 +++++++
 components/lwip/lwip/src/core/ipv4/dhcp.c       | 9 +++++++++
 components/lwip/port/esp8266/include/lwipopts.h | 9 +++++++++
 3 files changed, 25 insertions(+)

diff --git a/components/lwip/Kconfig b/components/lwip/Kconfig
index a215839e..b5ab8284 100644
--- a/components/lwip/Kconfig
+++ b/components/lwip/Kconfig
@@ -229,6 +229,13 @@ config LWIP_DHCPS_MAX_STATION_NUM
         After this number is exceeded, DHCP server removes of the oldest device
         from it's address pool, without notification.
 
+config LWIP_DHCP_DISCOVER_RETRANSMISSION_INTERVAL
+    int "DHCP discover retransmission interval (milliseconds)"
+    default 250 # 4 * default retransmission interval
+    range 250 1000
+    help
+        Set time interval of retransmissions of DHCP discover.
+
 endmenu #DHCP
 
 menuconfig LWIP_AUTOIP
diff --git a/components/lwip/lwip/src/core/ipv4/dhcp.c b/components/lwip/lwip/src/core/ipv4/dhcp.c
index 7590b6bc..a916c2ea 100644
--- a/components/lwip/lwip/src/core/ipv4/dhcp.c
+++ b/components/lwip/lwip/src/core/ipv4/dhcp.c
@@ -1007,7 +1007,16 @@ dhcp_discover(struct netif *netif)
     autoip_start(netif);
   }
 #endif /* LWIP_DHCP_AUTOIP_COOP */
+
+#if ESP_DHCP
+/** 
+ * Since for embedded devices it's not that hard to miss a discover packet, so lower
+ * the discover retry backoff time from (2,4,8,16,32,60,60)s to (500m,1,2,4,8,15,15)s.
+ */
+  msecs = (dhcp->tries < 6 ? 1 << dhcp->tries : 60) * LWIP_DHCP_DISCOVER_RETRANSMISSION_INTERVAL;
+#else
   msecs = (dhcp->tries < 6 ? 1 << dhcp->tries : 60) * 1000;
+#endif
   dhcp->request_timeout = (msecs + DHCP_FINE_TIMER_MSECS - 1) / DHCP_FINE_TIMER_MSECS;
   LWIP_DEBUGF(DHCP_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_STATE, ("dhcp_discover(): set request timeout %"U16_F" msecs\n", msecs));
   return result;
diff --git a/components/lwip/port/esp8266/include/lwipopts.h b/components/lwip/port/esp8266/include/lwipopts.h
index 30ffdf31..07db6ed5 100644
--- a/components/lwip/port/esp8266/include/lwipopts.h
+++ b/components/lwip/port/esp8266/include/lwipopts.h
@@ -54,6 +54,7 @@
 
 #define ESP_LWIP 1
 #define ESP_IP4_ATON 1
+#define ESP_DHCP 1
 
 #ifdef CONFIG_ESP_DNS
 #define ESP_DNS  1
@@ -720,6 +721,14 @@ size_t memp_malloc_get_size(size_t type);
  * (up to the maximum limit defined here).
  */
 #define LWIP_DHCP_MAX_DNS_SERVERS       DNS_MAX_SERVERS
+
+/**
+ * LWIP_DHCP_DISCOVER_RETRANSMISSION_INTERVAL: DHCP discover retry backoff time. 
+ * (default is 250, a conservative default, the maximum is 1000.)
+ * Since for embedded devices it's not that hard to miss a discover packet, so 
+ * it is necessary to reduce the discovery retry backoff time.
+ */
+#define LWIP_DHCP_DISCOVER_RETRANSMISSION_INTERVAL       CONFIG_LWIP_DHCP_DISCOVER_RETRANSMISSION_INTERVAL
 /**
  * @}
  */