dhcpcd-discuss

Hi Guy

On Tuesday 30 August 2016 20:46:55 Guy Yur wrote:
> dhcpcd with the patch no longer crashes on the above sequence.

yay!

> What should happen to the IPv4 address when the interface
> goes down or when the link is lost?
> 
> Before the patch,
> 1. ifconfig lan0 down
> ifconfig lan0 -> ipv4 address from dhcp was removed
> 2. ifconfig lan0 up
> ifconfig lan0 -> ipv4 address from dhcp was not restored (waited one minute)
> 
> 1. link disconnected on lan0
> ifconfig lan0 -> ipv4 address from dhcp was removed
> 2. link reconnected on lan0
> ifconfig lan0 -> ipv4 address from dhcp was added after a few seconds
> 
> 
> After the patch,
> 1. ifconfig lan0 down
> ifconfig lan0 -> ipv4 address from dhcp was not removed
> 2. ifconfig lan0 up
> 
> 1. link disconnected on lan0
> ifconfig lan0 -> ipv4 address from dhcp was not removed
> 2. link reconnected on lan0

In both cases the address should be restored at the last step.
I will try and test more on BSD tomorrow.

One potential problem is that ifa_msghdr does not carry the PID of the 
originating process which deleted the address and if there is a delay 
receiving it, dhcpcd can get confused.

We may have to extend the kernel structure so it can carry the pid to make it 
a lot tighter.

Attached is a new dhcpcd patch which may help.
Let me know.

Roy

Index: dhcp.c
==================================================================
--- dhcp.c
+++ dhcp.c
@@ -3651,13 +3651,16 @@
 	state = D_STATE(ifp);
 	if (state == NULL)
 		return;
 
 	if (cmd == RTM_DELADDR) {
-		if (IPV4_BRD_EQ(state->addr, ia)) {
+		if (state->addr == ia) {
 			logger(ifp->ctx, LOG_INFO,
 			    "%s: deleted IP address %s", ifp->name, ia->saddr);
+			state->addr = NULL;
+			/* Don't clear the added state as we need
+			 * to drop the lease. */
 			dhcp_drop(ifp, "EXPIRE");
 		}
 		return;
 	}
 

Index: ipv4.c
==================================================================
--- ipv4.c
+++ ipv4.c
@@ -894,11 +894,14 @@
 	struct if_options *ifo;
 	struct dhcp_state *state;
 
 	state = D_STATE(ifp);
 	ifo = ifp->options;
-	if (ifo->options & DHCPCD_INFORM ||
+	/* The lease could have been added, but the address deleted
+	 * by a 3rd party. */
+	if (state->addr == NULL ||
+	    ifo->options & DHCPCD_INFORM ||
 	    (ifo->options & DHCPCD_STATIC && ifo->req_addr.s_addr == 0))
 		return 0;
 	r = ipv4_deladdr(state->addr, 0);
 	return r;
 }