Fix iteration after expiring a list entry

After removing an entry, the next entry will be at the same offset as
the entry we just removed.  Also the total length will have changed.

Update the length when we remove an entry, and advance the offset only
when we don't.

Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

src/odhcp6c.c

@@ -619,7 +619,7 @@ static void odhcp6c_expire_list(enum odhcp6c_state state, uint32_t elapsed)
 	uint8_t *start = odhcp6c_get_state(state, &len);
 	for (struct odhcp6c_entry *c = (struct odhcp6c_entry*)start;
 			(uint8_t*)c < &start[len] && &c->auxtarget[c->auxlen] <= &start[len];
-			c = (struct odhcp6c_entry*)(&c->auxtarget[c->auxlen])) {
+			) {
 		if (c->t1 < elapsed)
 			c->t1 = 0;
 		else if (c->t1 != UINT32_MAX)
@@ -640,8 +640,12 @@ static void odhcp6c_expire_list(enum odhcp6c_state state, uint32_t elapsed)
 		else if (c->valid != UINT32_MAX)
 			c->valid -= elapsed;
 
-		if (!c->valid)
+		if (!c->valid) {
 			odhcp6c_remove_state(state, ((uint8_t*)c) - start, sizeof(*c) + c->auxlen);
+			start = odhcp6c_get_state(state, &len);
+		} else {
+			c = (struct odhcp6c_entry*)(&c->auxtarget[c->auxlen]);
+		}
 	}
 }