ipv4/igmp: fix v1/v2 switchback timeout based on rfc3376, 8.12

Similiar with ipv6 mcast commit 89225d1 ("net: ipv6: mld: fix v1/v2
switchback timeout to rfc3810, 9.12.")

i) RFC3376 8.12. Older Version Querier Present Timeout says:

   The Older Version Querier Interval is the time-out for transitioning
   a host back to IGMPv3 mode once an older version query is heard.
   When an older version query is received, hosts set their Older
   Version Querier Present Timer to Older Version Querier Interval.

   This value MUST be ((the Robustness Variable) times (the Query
   Interval in the last Query received)) plus (one Query Response
   Interval).

Currently we only use a hardcode value IGMP_V1/v2_ROUTER_PRESENT_TIMEOUT.
Fix it by adding two new items mr_qi(Query Interval) and mr_qri(Query Response
Interval) in struct in_device.

Now we can calculate the switchback time via (mr_qrv * mr_qi) + mr_qri.
We need update these values when receive IGMPv3 queries.

Reported-by: Ying Xu <yinxu@redhat.com>
Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/inetdevice.h

@@ -37,7 +37,9 @@ struct in_device {
 	unsigned long		mr_v1_seen;
 	unsigned long		mr_v2_seen;
 	unsigned long		mr_maxdelay;
-	unsigned char		mr_qrv;
+	unsigned long		mr_qi;		/* Query Interval */
+	unsigned long		mr_qri;		/* Query Response Interval */
+	unsigned char		mr_qrv;		/* Query Robustness Variable */
 	unsigned char		mr_gq_running;
 	unsigned char		mr_ifc_count;
 	struct timer_list	mr_gq_timer;	/* general query timer */

net/ipv4/igmp.c

@@ -111,13 +111,10 @@
 #ifdef CONFIG_IP_MULTICAST
 /* Parameter names and values are taken from igmp-v2-06 draft */
 
-#define IGMP_V1_ROUTER_PRESENT_TIMEOUT		(400*HZ)
-#define IGMP_V2_ROUTER_PRESENT_TIMEOUT		(400*HZ)
 #define IGMP_V2_UNSOLICITED_REPORT_INTERVAL	(10*HZ)
 #define IGMP_V3_UNSOLICITED_REPORT_INTERVAL	(1*HZ)
+#define IGMP_QUERY_INTERVAL			(125*HZ)
 #define IGMP_QUERY_RESPONSE_INTERVAL		(10*HZ)
-#define IGMP_QUERY_ROBUSTNESS_VARIABLE		2
-
 
 #define IGMP_INITIAL_REPORT_DELAY		(1)
 
@@ -935,13 +932,15 @@ static bool igmp_heard_query(struct in_device *in_dev, struct sk_buff *skb,
 
 			max_delay = IGMP_QUERY_RESPONSE_INTERVAL;
 			in_dev->mr_v1_seen = jiffies +
-				IGMP_V1_ROUTER_PRESENT_TIMEOUT;
+				(in_dev->mr_qrv * in_dev->mr_qi) +
+				in_dev->mr_qri;
 			group = 0;
 		} else {
 			/* v2 router present */
 			max_delay = ih->code*(HZ/IGMP_TIMER_SCALE);
 			in_dev->mr_v2_seen = jiffies +
-				IGMP_V2_ROUTER_PRESENT_TIMEOUT;
+				(in_dev->mr_qrv * in_dev->mr_qi) +
+				in_dev->mr_qri;
 		}
 		/* cancel the interface change timer */
 		in_dev->mr_ifc_count = 0;
@@ -981,8 +980,21 @@ static bool igmp_heard_query(struct in_device *in_dev, struct sk_buff *skb,
 		if (!max_delay)
 			max_delay = 1;	/* can't mod w/ 0 */
 		in_dev->mr_maxdelay = max_delay;
-		if (ih3->qrv)
-			in_dev->mr_qrv = ih3->qrv;
+
+		/* RFC3376, 4.1.6. QRV and 4.1.7. QQIC, when the most recently
+		 * received value was zero, use the default or statically
+		 * configured value.
+		 */
+		in_dev->mr_qrv = ih3->qrv ?: net->ipv4.sysctl_igmp_qrv;
+		in_dev->mr_qi = IGMPV3_QQIC(ih3->qqic)*HZ ?: IGMP_QUERY_INTERVAL;
+
+		/* RFC3376, 8.3. Query Response Interval:
+		 * The number of seconds represented by the [Query Response
+		 * Interval] must be less than the [Query Interval].
+		 */
+		if (in_dev->mr_qri >= in_dev->mr_qi)
+			in_dev->mr_qri = (in_dev->mr_qi/HZ - 1)*HZ;
+
 		if (!group) { /* general query */
 			if (ih3->nsrcs)
 				return true;	/* no sources allowed */
@@ -1723,18 +1735,30 @@ void ip_mc_down(struct in_device *in_dev)
 	ip_mc_dec_group(in_dev, IGMP_ALL_HOSTS);
 }
 
-void ip_mc_init_dev(struct in_device *in_dev)
-{
 #ifdef CONFIG_IP_MULTICAST
+static void ip_mc_reset(struct in_device *in_dev)
+{
 	struct net *net = dev_net(in_dev->dev);
+
+	in_dev->mr_qi = IGMP_QUERY_INTERVAL;
+	in_dev->mr_qri = IGMP_QUERY_RESPONSE_INTERVAL;
+	in_dev->mr_qrv = net->ipv4.sysctl_igmp_qrv;
+}
+#else
+static void ip_mc_reset(struct in_device *in_dev)
+{
+}
 #endif
+
+void ip_mc_init_dev(struct in_device *in_dev)
+{
 	ASSERT_RTNL();
 
 #ifdef CONFIG_IP_MULTICAST
 	timer_setup(&in_dev->mr_gq_timer, igmp_gq_timer_expire, 0);
 	timer_setup(&in_dev->mr_ifc_timer, igmp_ifc_timer_expire, 0);
-	in_dev->mr_qrv = net->ipv4.sysctl_igmp_qrv;
 #endif
+	ip_mc_reset(in_dev);
 
 	spin_lock_init(&in_dev->mc_tomb_lock);
 }
@@ -1744,15 +1768,10 @@ void ip_mc_init_dev(struct in_device *in_dev)
 void ip_mc_up(struct in_device *in_dev)
 {
 	struct ip_mc_list *pmc;
-#ifdef CONFIG_IP_MULTICAST
-	struct net *net = dev_net(in_dev->dev);
-#endif
 
 	ASSERT_RTNL();
 
-#ifdef CONFIG_IP_MULTICAST
-	in_dev->mr_qrv = net->ipv4.sysctl_igmp_qrv;
-#endif
+	ip_mc_reset(in_dev);
 	ip_mc_inc_group(in_dev, IGMP_ALL_HOSTS);
 
 	for_each_pmc_rtnl(in_dev, pmc) {