Don't reset default route when something else had changed it

[mcspr]

ref. esp8266/Arduino#7148 esp8266/Arduino#8317

Current implementation resets default route regardless of it's contents:

esp82xx-nonos-linklayer/glue-lwip/lwip-git.c

Lines 322 to 326 in 18975ca

	if ( netif->flags & NETIF_FLAG_UP
	&& netif == netif_sta)
	{
	// this is our default route
	netif_set_default(netif);

But, it does respect un-setting it:

esp82xx-nonos-linklayer/glue-lwip/lwip-git.c

Lines 525 to 526 in 18975ca

	if (netif_default == &netif_git[netif_idx])
	netif_set_default(NULL);

Should it respect the already-set netif?

diff --git a/glue-lwip/lwip-git.c b/glue-lwip/lwip-git.c
index 4cf133f..b3afc4d 100644
--- a/glue-lwip/lwip-git.c
+++ b/glue-lwip/lwip-git.c
@@ -322,8 +322,10 @@ static void netif_sta_status_callback (struct netif* netif)
        if (   netif->flags & NETIF_FLAG_UP
            && netif == netif_sta)
        {
-               // this is our default route
-               netif_set_default(netif);
+               // this is our default route, but only when there is nothing else
+               if (netif_default == NULL) {
+                       netif_set_default(netif);
+               }

                // If we have a valid address of any type restart SNTP
                bool valid_address = ip_2_ip4(&netif->ip_addr)->addr;

If yes, Core's Lwip class also needs a patch of the same nature

[d-a-v]

fixed by #54

esp82xx-nonos-linklayer/glue-lwip/lwip-git.c

Line 325 in 450bb63

if ((netif_default == NULL) && !ip_addr_isany(&netif->gw)) {