From e1b11c518aded9136b4f44759c6e2a6be4161ee9 Mon Sep 17 00:00:00 2001
From: Steven Barth <steven@midlink.org>
Date: Wed, 23 Oct 2013 10:13:00 +0200
Subject: [PATCH] Avoid updating too often if ISP spams RAs

---
 src/odhcp6c.c | 13 ++++++++++---
 src/odhcp6c.h |  4 ++--
 src/ra.c      | 13 +++++++------
 3 files changed, 19 insertions(+), 11 deletions(-)

diff --git a/src/odhcp6c.c b/src/odhcp6c.c
index 5c433af..e81b15f 100644
--- a/src/odhcp6c.c
+++ b/src/odhcp6c.c
@@ -463,17 +463,23 @@ struct odhcp6c_entry* odhcp6c_find_entry(enum odhcp6c_state state, const struct
 }
 
 
-void odhcp6c_update_entry_safe(enum odhcp6c_state state, struct odhcp6c_entry *new, uint32_t safe)
+bool odhcp6c_update_entry_safe(enum odhcp6c_state state, struct odhcp6c_entry *new, uint32_t safe)
 {
 	size_t len;
 	struct odhcp6c_entry *x = odhcp6c_find_entry(state, new);
 	struct odhcp6c_entry *start = odhcp6c_get_state(state, &len);
+	bool changed = true;
 
 	if (x && x->valid > new->valid && new->valid < safe)
 		new->valid = safe;
 
 	if (new->valid > 0) {
 		if (x) {
+			if (new->valid >= x->valid && new->valid - x->valid < 60 &&
+					new->preferred >= x->preferred &&
+					new->preferred - x->preferred < 60 &&
+					x->class == new->class)
+				changed = false;
 			x->valid = new->valid;
 			x->preferred = new->preferred;
 			x->class = new->class;
@@ -483,12 +489,13 @@ void odhcp6c_update_entry_safe(enum odhcp6c_state state, struct odhcp6c_entry *n
 	} else if (x) {
 		odhcp6c_remove_state(state, (x - start) * sizeof(*x), sizeof(*x));
 	}
+	return changed;
 }
 
 
-void odhcp6c_update_entry(enum odhcp6c_state state, struct odhcp6c_entry *new)
+bool odhcp6c_update_entry(enum odhcp6c_state state, struct odhcp6c_entry *new)
 {
-	odhcp6c_update_entry_safe(state, new, 0);
+	return odhcp6c_update_entry_safe(state, new, 0);
 }
 
 
diff --git a/src/odhcp6c.h b/src/odhcp6c.h
index 669b33d..61dee63 100644
--- a/src/odhcp6c.h
+++ b/src/odhcp6c.h
@@ -250,8 +250,8 @@ void* odhcp6c_get_state(enum odhcp6c_state state, size_t *len);
 
 // Entry manipulation
 struct odhcp6c_entry* odhcp6c_find_entry(enum odhcp6c_state state, const struct odhcp6c_entry *new);
-void odhcp6c_update_entry(enum odhcp6c_state state, struct odhcp6c_entry *new);
-void odhcp6c_update_entry_safe(enum odhcp6c_state state, struct odhcp6c_entry *new, uint32_t safe);
+bool odhcp6c_update_entry(enum odhcp6c_state state, struct odhcp6c_entry *new);
+bool odhcp6c_update_entry_safe(enum odhcp6c_state state, struct odhcp6c_entry *new, uint32_t safe);
 
 void odhcp6c_expire(void);
 uint32_t odhcp6c_elapsed(void);
diff --git a/src/ra.c b/src/ra.c
index 83f1758..f41602a 100644
--- a/src/ra.c
+++ b/src/ra.c
@@ -120,6 +120,7 @@ static void update_proc(const char *sect, const char *opt, uint32_t value)
 bool ra_process(void)
 {
 	bool found = false;
+	bool changed = false;
 	uint8_t buf[1500], cmsg_buf[128];
 	struct nd_router_advert *adv = (struct nd_router_advert*)buf;
 	struct odhcp6c_entry entry = {IN6ADDR_ANY_INIT, 0, 0, IN6ADDR_ANY_INIT, 0, 0, 0};
@@ -183,7 +184,7 @@ bool ra_process(void)
 			entry.priority = pref_to_priority(0);
 		entry.valid = router_valid;
 		entry.preferred = entry.valid;
-		odhcp6c_update_entry(STATE_RA_ROUTE, &entry);
+		changed |= odhcp6c_update_entry(STATE_RA_ROUTE, &entry);
 
 		// Parse ND parameters
 		if (ntohl(adv->nd_ra_reachable) <= 3600000)
@@ -215,7 +216,7 @@ bool ra_process(void)
 					continue;
 
 				if (entry.priority > 0)
-					odhcp6c_update_entry(STATE_RA_ROUTE, &entry);
+					changed |= odhcp6c_update_entry(STATE_RA_ROUTE, &entry);
 			} else if (opt->type == ND_OPT_PREFIX_INFORMATION && opt->len == 4) {
 				struct nd_opt_prefix_info *pinfo = (struct nd_opt_prefix_info*)opt;
 				entry.router = any;
@@ -232,7 +233,7 @@ bool ra_process(void)
 					continue;
 
 				if (pinfo->nd_opt_pi_flags_reserved & ND_OPT_PI_FLAG_ONLINK)
-					odhcp6c_update_entry_safe(STATE_RA_ROUTE, &entry, 7200);
+					changed |= odhcp6c_update_entry_safe(STATE_RA_ROUTE, &entry, 7200);
 
 				if (!(pinfo->nd_opt_pi_flags_reserved & ND_OPT_PI_FLAG_AUTO) ||
 						pinfo->nd_opt_pi_prefix_len != 64)
@@ -241,7 +242,7 @@ bool ra_process(void)
 				entry.target.s6_addr32[2] = lladdr.s6_addr32[2];
 				entry.target.s6_addr32[3] = lladdr.s6_addr32[3];
 
-				odhcp6c_update_entry_safe(STATE_RA_PREFIX, &entry, 7200);
+				changed |= odhcp6c_update_entry_safe(STATE_RA_PREFIX, &entry, 7200);
 			} else if (opt->type == ND_OPT_RECURSIVE_DNS && opt->len > 2) {
 				entry.router = from.sin6_addr;
 				entry.priority = 0;
@@ -253,7 +254,7 @@ bool ra_process(void)
 				for (ssize_t i = 0; i < (opt->len - 1) / 2; ++i) {
 					memcpy(&entry.target, &opt->data[6 + i * sizeof(entry.target)],
 							sizeof(entry.target));
-					odhcp6c_update_entry(STATE_RA_DNS, &entry);
+					changed |= odhcp6c_update_entry(STATE_RA_DNS, &entry);
 				}
 			}
 		}
@@ -269,5 +270,5 @@ bool ra_process(void)
 	if (found)
 		odhcp6c_expire();
 
-	return found;
+	return found && changed;
 }
-- 
2.39.2