[PATCH 2/4] ipv6: mld: rename mldv2_mrc() and add mldv2_qqi()

[Ujjal Roy <royujjal@gmail.com>]

Rename mldv2_mrc() to mldv2_mrd() as it used to calculate
the Maximum Response Delay from the Maximum Response Code.

Introduce a new API mldv2_qqi() to define the existing
calculation logic of QQI from QQIC. This also organizes
the existing mld_update_qi() API.

Added by e3f5b1704 ("net: ipv6: mld: get rid of MLDV2_MRC and simplify calculation").

Signed-off-by: Ujjal Roy <royujjal@gmail.com>
---
 include/net/mld.h         | 64 +++++++++++++++++++++++++++++++++------
 net/bridge/br_multicast.c |  2 +-
 net/ipv6/mcast.c          | 19 ++----------
 3 files changed, 58 insertions(+), 27 deletions(-)

diff --git a/include/net/mld.h b/include/net/mld.h
index c07359808493..6373eb76efe5 100644
--- a/include/net/mld.h
+++ b/include/net/mld.h
@@ -89,29 +89,73 @@ struct mld2_query {
 #define MLDV2_QQIC_EXP(value)	(((value) >> 4) & 0x07)
 #define MLDV2_QQIC_MAN(value)	((value) & 0x0f)
 
-#define MLD_EXP_MIN_LIMIT	32768UL
-#define MLDV1_MRD_MAX_COMPAT	(MLD_EXP_MIN_LIMIT - 1)
+#define MLD_QQIC_MIN_THRESHOLD	128
+#define MLD_MRC_MIN_THRESHOLD	32768UL
+#define MLDV1_MRD_MAX_COMPAT	(MLD_MRC_MIN_THRESHOLD - 1)
 
 #define MLD_MAX_QUEUE		8
 #define MLD_MAX_SKBS		32
 
-static inline unsigned long mldv2_mrc(const struct mld2_query *mlh2)
-{
-	/* RFC3810, 5.1.3. Maximum Response Code */
-	unsigned long ret, mc_mrc = ntohs(mlh2->mld2q_mrc);
+/* V2 exponential field decoding */
 
-	if (mc_mrc < MLD_EXP_MIN_LIMIT) {
-		ret = mc_mrc;
+/* Calculate Maximum Response Delay from Maximum Response Code
+ *
+ * RFC3810, 5.1.3. defines the decoding formula:
+ *      0 1 2 3 4 5 6 7 8 9 A B C D E F
+ *     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ *     |1| exp |          mant         |
+ *     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * Maximum Response Delay = (mant | 0x1000) << (exp+3)
+ */
+static inline unsigned long mldv2_mrd(const struct mld2_query *mlh2)
+{
+	/* RFC3810, relevant sections:
+	 *  - 5.1.3. Maximum Response Code
+	 *  - 9.3. Query Response Interval
+	 */
+	unsigned long mc_mrc = ntohs(mlh2->mld2q_mrc);
+
+	if (mc_mrc < MLD_MRC_MIN_THRESHOLD) {
+		return mc_mrc;
 	} else {
 		unsigned long mc_man, mc_exp;
 
 		mc_exp = MLDV2_MRC_EXP(mc_mrc);
 		mc_man = MLDV2_MRC_MAN(mc_mrc);
 
-		ret = (mc_man | 0x1000) << (mc_exp + 3);
+		return ((mc_man | 0x1000) << (mc_exp + 3));
 	}
+}
 
-	return ret;
+/* Calculate Querier's Query Interval from Querier's Query Interval Code
+ *
+ * RFC3810, 5.1.9. defines the decoding formula:
+ *      0 1 2 3 4 5 6 7
+ *     +-+-+-+-+-+-+-+-+
+ *     |1| exp | mant  |
+ *     +-+-+-+-+-+-+-+-+
+ * QQI = (mant | 0x10) << (exp + 3)
+ */
+static inline unsigned long mldv2_qqi(const struct mld2_query *mlh2)
+{
+	/* RFC3810, relevant sections:
+	 *  - 5.1.9. QQIC (Querier's Query Interval Code)
+	 *  - 9.2. Query Interval
+	 *  - 9.12. Older Version Querier Present Timeout
+	 *    (the [Query Interval] in the last Query received)
+	 */
+	unsigned long qqic = ntohs(mlh2->mld2q_qqic);
+
+	if (qqic < MLD_QQIC_MIN_THRESHOLD) {
+		return qqic;
+	} else {
+		unsigned long mc_man, mc_exp;
+
+		mc_exp = MLDV2_QQIC_EXP(qqic);
+		mc_man = MLDV2_QQIC_MAN(qqic);
+
+		return ((mc_man | 0x10) << (mc_exp + 3));
+	}
 }
 
 #endif
diff --git a/net/bridge/br_multicast.c b/net/bridge/br_multicast.c
index 9fec76e887bc..1438c023db62 100644
--- a/net/bridge/br_multicast.c
+++ b/net/bridge/br_multicast.c
@@ -3606,7 +3606,7 @@ static int br_ip6_multicast_query(struct net_bridge_mcast *brmctx,
 		    mld2q->mld2q_suppress)
 			goto out;
 
-		max_delay = max(msecs_to_jiffies(mldv2_mrc(mld2q)), 1UL);
+		max_delay = max(msecs_to_jiffies(mldv2_mrd(mld2q)), 1UL);
 	}
 
 	is_general_query = group && ipv6_addr_any(group);
diff --git a/net/ipv6/mcast.c b/net/ipv6/mcast.c
index 3330adcf26db..6ddc18ac59b9 100644
--- a/net/ipv6/mcast.c
+++ b/net/ipv6/mcast.c
@@ -1315,20 +1315,7 @@ static void mld_update_qi(struct inet6_dev *idev,
 	 *  - 9.12. Older Version Querier Present Timeout
 	 *    (the [Query Interval] in the last Query received)
 	 */
-	unsigned long mc_qqi;
-
-	if (mlh2->mld2q_qqic < 128) {
-		mc_qqi = mlh2->mld2q_qqic;
-	} else {
-		unsigned long mc_man, mc_exp;
-
-		mc_exp = MLDV2_QQIC_EXP(mlh2->mld2q_qqic);
-		mc_man = MLDV2_QQIC_MAN(mlh2->mld2q_qqic);
-
-		mc_qqi = (mc_man | 0x10) << (mc_exp + 3);
-	}
-
-	idev->mc_qi = mc_qqi * HZ;
+	idev->mc_qi = mldv2_qqi(mlh2) * HZ;
 }
 
 static void mld_update_qri(struct inet6_dev *idev,
@@ -1338,7 +1325,7 @@ static void mld_update_qri(struct inet6_dev *idev,
 	 *  - 5.1.3. Maximum Response Code
 	 *  - 9.3. Query Response Interval
 	 */
-	idev->mc_qri = msecs_to_jiffies(mldv2_mrc(mlh2));
+	idev->mc_qri = msecs_to_jiffies(mldv2_mrd(mlh2));
 }
 
 static int mld_process_v1(struct inet6_dev *idev, struct mld_msg *mld,
@@ -1390,7 +1377,7 @@ static int mld_process_v1(struct inet6_dev *idev, struct mld_msg *mld,
 static void mld_process_v2(struct inet6_dev *idev, struct mld2_query *mld,
 			   unsigned long *max_delay)
 {
-	*max_delay = max(msecs_to_jiffies(mldv2_mrc(mld)), 1UL);
+	*max_delay = max(msecs_to_jiffies(mldv2_mrd(mld)), 1UL);
 
 	mld_update_qrv(idev, mld);
 	mld_update_qi(idev, mld);
-- 
2.43.0