diff mbox

[RFCv2,3/4] batman-adv: Forward IGMP/MLD reports to selected querier (only)

Message ID 1427875479-9240-4-git-send-email-linus.luessing@c0d3.blue
State RFC, archived
Headers show

Commit Message

Linus Lüssing April 1, 2015, 8:04 a.m. UTC
With this patch IGMP or MLD reports are only forwarded to the selected
IGMP/MLD querier as RFC4541 suggests. This is necessary to avoid
multicast packet loss in bridged scenarios later:

An IGMPv2/MLDv1 querier does not actively join the multicast group the
reports are sent to. Because of this, this leads to snooping
bridges/switches not being able to learn of multicast listeners in the
mesh and wrongly shutting down ports for multicast traffic to the mesh.
---
 net/batman-adv/main.h           |    6 +-
 net/batman-adv/multicast.c      |  248 ++++++++++++++++++++++++++++++++++++++-
 net/batman-adv/multicast.h      |    8 ++
 net/batman-adv/soft-interface.c |   11 ++
 net/batman-adv/types.h          |   14 +++
 5 files changed, 280 insertions(+), 7 deletions(-)

Comments

David Miller April 1, 2015, 5:44 p.m. UTC | #1
From: Linus Lüssing <linus.luessing@c0d3.blue>
Date: Wed,  1 Apr 2015 10:04:38 +0200

> With this patch IGMP or MLD reports are only forwarded to the selected
> IGMP/MLD querier as RFC4541 suggests. This is necessary to avoid
> multicast packet loss in bridged scenarios later:
> 
> An IGMPv2/MLDv1 querier does not actively join the multicast group the
> reports are sent to. Because of this, this leads to snooping
> bridges/switches not being able to learn of multicast listeners in the
> mesh and wrongly shutting down ports for multicast traffic to the mesh.

There is no way this is going to work.

First of all, you have no proper Kconfig dependencies upon IPV6, yet
you are calling these newly exported ipv6 multicast interfaces
unconditionally.

Even once you resolve that, you are going to run into problems in
situations where BATMAN_ADV=y and IPV6=m, for example.
diff mbox

Patch

diff --git a/net/batman-adv/main.h b/net/batman-adv/main.h
index 4d23188..b6d3a73 100644
--- a/net/batman-adv/main.h
+++ b/net/batman-adv/main.h
@@ -178,9 +178,11 @@  enum batadv_uev_type {
 #include <net/addrconf.h>	/* ipv6 address stuff */
 #include <linux/ip.h>
 #include <net/rtnetlink.h>
+#include <net/mld.h>
 #include <linux/jiffies.h>
 #include <linux/seq_file.h>
 #include <linux/if_vlan.h>
+#include <linux/igmp.h>
 
 #include "types.h"
 
@@ -221,6 +223,7 @@  __be32 batadv_skb_crc32(struct sk_buff *skb, u8 *payload_ptr);
  * @BATADV_DBG_BLA: bridge loop avoidance messages
  * @BATADV_DBG_DAT: ARP snooping and DAT related messages
  * @BATADV_DBG_NC: network coding related messages
+ * @BATADV_DBG_MCAST: multicast related messages
  * @BATADV_DBG_ALL: the union of all the above log levels
  */
 enum batadv_dbg_level {
@@ -230,7 +233,8 @@  enum batadv_dbg_level {
 	BATADV_DBG_BLA    = BIT(3),
 	BATADV_DBG_DAT    = BIT(4),
 	BATADV_DBG_NC	  = BIT(5),
-	BATADV_DBG_ALL    = 63,
+	BATADV_DBG_MCAST  = BIT(6),
+	BATADV_DBG_ALL    = 127,
 };
 
 #ifdef CONFIG_BATMAN_ADV_DEBUG
diff --git a/net/batman-adv/multicast.c b/net/batman-adv/multicast.c
index b24e4bb..055f55b 100644
--- a/net/batman-adv/multicast.c
+++ b/net/batman-adv/multicast.c
@@ -247,10 +247,76 @@  out:
 }
 
 /**
+ * batadv_mcast_is_report_ipv4 - check for IGMP reports (and queries)
+ * @bat_priv: the bat priv with all the soft interface information
+ * @skb: the ethernet frame destined for the mesh
+ * @orig: if IGMP report: to be set to the querier to forward the skb to
+ *
+ * Checks whether the given frame is an IGMP report and if so sets the
+ * orig pointer to the originator of the selected IGMP querier if one exists
+ * and returns true. Otherwise returns false.
+ *
+ * If the packet is a general IGMP query instead then we delete the memorized,
+ * foreign IGMP querier (if one exists): We became the selected querier and
+ * therefore do not need to forward reports into the mesh.
+ *
+ * This call might reallocate skb data.
+ */
+static bool batadv_mcast_is_report_ipv4(struct batadv_priv *bat_priv,
+					struct sk_buff *skb,
+					struct batadv_orig_node **orig)
+{
+	struct batadv_mcast_querier_state *querier;
+	struct batadv_orig_node *orig_node;
+
+	if (ip_mc_check_igmp(skb, NULL) < 0)
+		return false;
+
+	querier = &bat_priv->mcast.querier_ipv4;
+
+	switch (igmp_hdr(skb)->type) {
+	case IGMP_HOST_MEMBERSHIP_REPORT:
+	case IGMPV2_HOST_MEMBERSHIP_REPORT:
+	case IGMPV3_HOST_MEMBERSHIP_REPORT:
+		rcu_read_lock();
+		orig_node = rcu_dereference(querier->orig);
+		if (orig_node && atomic_inc_not_zero(&orig_node->refcount)) {
+			/* TODO: include multicast routers via MRD (RFC4286) */
+			batadv_dbg(BATADV_DBG_MCAST, bat_priv,
+				   "Redirecting IGMP Report to %pM\n",
+				   orig_node->orig);
+			*orig = orig_node;
+		}
+		rcu_read_unlock();
+
+		return true;
+	case IGMP_HOST_MEMBERSHIP_QUERY:
+		/* RFC4541, section 2.1.1.1.b) says:
+		 * ignore general queries from 0.0.0.0
+		 */
+		if (!ip_hdr(skb)->saddr || igmp_hdr(skb)->group)
+			break;
+
+		spin_lock_bh(&querier->orig_lock);
+		orig_node = rcu_dereference(querier->orig);
+		if (orig_node)
+			rcu_assign_pointer(querier->orig, NULL);
+		spin_unlock_bh(&querier->orig_lock);
+
+		batadv_dbg(BATADV_DBG_MCAST, bat_priv,
+			   "Snooped own IGMP Query\n");
+		break;
+	}
+
+	return false;
+}
+
+/**
  * batadv_mcast_forw_mode_check_ipv4 - check for optimized forwarding potential
  * @bat_priv: the bat priv with all the soft interface information
  * @skb: the IPv4 packet to check
  * @is_unsnoopable: stores whether the destination is snoopable
+ * @orig: for IGMP reports: to be set to the querier to forward the skb to
  *
  * Checks whether the given IPv4 packet has the potential to be forwarded with a
  * mode more optimal than classic flooding.
@@ -260,7 +326,8 @@  out:
  */
 static int batadv_mcast_forw_mode_check_ipv4(struct batadv_priv *bat_priv,
 					     struct sk_buff *skb,
-					     bool *is_unsnoopable)
+					     bool *is_unsnoopable,
+					     struct batadv_orig_node **orig)
 {
 	struct iphdr *iphdr;
 
@@ -268,6 +335,9 @@  static int batadv_mcast_forw_mode_check_ipv4(struct batadv_priv *bat_priv,
 	if (!pskb_may_pull(skb, sizeof(struct ethhdr) + sizeof(*iphdr)))
 		return -ENOMEM;
 
+	if (batadv_mcast_is_report_ipv4(bat_priv, skb, orig))
+		return 0;
+
 	iphdr = ip_hdr(skb);
 
 	/* TODO: Implement Multicast Router Discovery (RFC4286),
@@ -285,10 +355,72 @@  static int batadv_mcast_forw_mode_check_ipv4(struct batadv_priv *bat_priv,
 }
 
 /**
+ * batadv_mcast_is_report_ipv6 - check for MLD reports (and queries)
+ * @bat_priv: the bat priv with all the soft interface information
+ * @skb: the ethernet frame destined for the mesh
+ * @orig: if MLD report: to be set to the querier to forward the skb to
+ *
+ * Checks whether the given frame is an MLD report and if so sets the
+ * orig pointer to the originator of the selected MLD querier if one exists
+ * and returns true. Otherwise returns false.
+ *
+ * If the packet is a general MLD query instead then we delete the memorized,
+ * foreign MLD querier (if one exists): We became the selected querier and
+ * therefore do not need to forward reports into the mesh.
+ *
+ * This call might reallocate skb data.
+ */
+static bool batadv_mcast_is_report_ipv6(struct batadv_priv *bat_priv,
+					struct sk_buff *skb,
+					struct batadv_orig_node **orig)
+{
+	struct mld_msg *mld;
+	struct batadv_mcast_querier_state *querier;
+	struct batadv_orig_node *orig_node;
+	int ret;
+
+	if (ipv6_mc_check_mld(skb, NULL) < 0)
+		return false;
+
+	querier = &bat_priv->mcast.querier_ipv6;
+	mld = (struct mld_msg *)icmp6_hdr(skb);
+
+	switch (mld->mld_type) {
+	case ICMPV6_MGM_REPORT:
+	case ICMPV6_MLD2_REPORT:
+		rcu_read_lock();
+		orig_node = rcu_dereference(querier->orig);
+		if (orig_node && atomic_inc_not_zero(&orig_node->refcount)) {
+			/* TODO: include multicast routers via MRD (RFC4286) */
+			batadv_dbg(BATADV_DBG_MCAST, bat_priv,
+				   "Redirecting MLD Report to %pM\n",
+				   orig_node->orig);
+			*orig = orig_node;
+		}
+		rcu_read_unlock();
+
+		return true;
+	case ICMPV6_MGM_QUERY:
+		spin_lock_bh(&querier->orig_lock);
+		orig_node = rcu_dereference(querier->orig);
+		if (orig_node)
+			rcu_assign_pointer(querier->orig, NULL);
+		spin_unlock_bh(&querier->orig_lock);
+
+		batadv_dbg(BATADV_DBG_MCAST, bat_priv,
+			   "Snooped own MLD Query\n");
+		break;
+	}
+
+	return false;
+}
+
+/**
  * batadv_mcast_forw_mode_check_ipv6 - check for optimized forwarding potential
  * @bat_priv: the bat priv with all the soft interface information
  * @skb: the IPv6 packet to check
  * @is_unsnoopable: stores whether the destination is snoopable
+ * @orig: for MLD reports: to be set to the querier to forward the skb to
  *
  * Checks whether the given IPv6 packet has the potential to be forwarded with a
  * mode more optimal than classic flooding.
@@ -298,7 +430,8 @@  static int batadv_mcast_forw_mode_check_ipv4(struct batadv_priv *bat_priv,
  */
 static int batadv_mcast_forw_mode_check_ipv6(struct batadv_priv *bat_priv,
 					     struct sk_buff *skb,
-					     bool *is_unsnoopable)
+					     bool *is_unsnoopable,
+					     struct batadv_orig_node **orig)
 {
 	struct ipv6hdr *ip6hdr;
 
@@ -306,6 +439,9 @@  static int batadv_mcast_forw_mode_check_ipv6(struct batadv_priv *bat_priv,
 	if (!pskb_may_pull(skb, sizeof(struct ethhdr) + sizeof(*ip6hdr)))
 		return -ENOMEM;
 
+	if (batadv_mcast_is_report_ipv6(bat_priv, skb, orig))
+		return 0;
+
 	ip6hdr = ipv6_hdr(skb);
 
 	/* TODO: Implement Multicast Router Discovery (RFC4286),
@@ -337,7 +473,8 @@  static int batadv_mcast_forw_mode_check_ipv6(struct batadv_priv *bat_priv,
  */
 static int batadv_mcast_forw_mode_check(struct batadv_priv *bat_priv,
 					struct sk_buff *skb,
-					bool *is_unsnoopable)
+					bool *is_unsnoopable,
+					struct batadv_orig_node **orig)
 {
 	struct ethhdr *ethhdr = eth_hdr(skb);
 
@@ -350,10 +487,10 @@  static int batadv_mcast_forw_mode_check(struct batadv_priv *bat_priv,
 	switch (ntohs(ethhdr->h_proto)) {
 	case ETH_P_IP:
 		return batadv_mcast_forw_mode_check_ipv4(bat_priv, skb,
-							 is_unsnoopable);
+							 is_unsnoopable, orig);
 	case ETH_P_IPV6:
 		return batadv_mcast_forw_mode_check_ipv6(bat_priv, skb,
-							 is_unsnoopable);
+							 is_unsnoopable, orig);
 	default:
 		return -EINVAL;
 	}
@@ -521,12 +658,16 @@  batadv_mcast_forw_mode(struct batadv_priv *bat_priv, struct sk_buff *skb,
 	bool is_unsnoopable = false;
 	struct ethhdr *ethhdr;
 
-	ret = batadv_mcast_forw_mode_check(bat_priv, skb, &is_unsnoopable);
+	ret = batadv_mcast_forw_mode_check(bat_priv, skb, &is_unsnoopable,
+					   orig);
 	if (ret == -ENOMEM)
 		return BATADV_FORW_NONE;
 	else if (ret < 0)
 		return BATADV_FORW_ALL;
 
+	if (*orig)
+		return BATADV_FORW_SINGLE;
+
 	ethhdr = eth_hdr(skb);
 
 	tt_count = batadv_tt_global_hash_count(bat_priv, ethhdr->h_dest,
@@ -558,6 +699,101 @@  batadv_mcast_forw_mode(struct batadv_priv *bat_priv, struct sk_buff *skb,
 }
 
 /**
+ * batadv_mcast_snoop_query_ipv4 - snoop for the selected MLD querier
+ * @skb: the unencapsulated ethernet frame coming from the mesh
+ * @orig_node: the originator this frame came from
+ *
+ * Checks whether the given frame is a general IGMP query from the selected
+ * querier and if so memorizes the originator this frame came from.
+ */
+static void batadv_mcast_snoop_query_ipv4(struct sk_buff *skb,
+					  struct batadv_orig_node *orig_node)
+{
+	struct batadv_mcast_querier_state *querier;
+
+	if (ip_mc_check_igmp(skb, NULL) < 0)
+		return;
+
+	/* we are only interested in general queries (group == 0.0.0.0) */
+	if (igmp_hdr(skb)->type != IGMP_HOST_MEMBERSHIP_QUERY ||
+	    igmp_hdr(skb)->group)
+		return;
+
+	/* RFC4541, section 2.1.1.1.b) says: ignore queries from 0.0.0.0 */
+	if (!ip_hdr(skb)->saddr)
+		return;
+
+	querier = &orig_node->bat_priv->mcast.querier_ipv4;
+
+	spin_lock_bh(&querier->orig_lock);
+	rcu_assign_pointer(querier->orig, orig_node);
+	spin_unlock_bh(&querier->orig_lock);
+
+	batadv_dbg(BATADV_DBG_MCAST, orig_node->bat_priv,
+		   "Snooped IGMP Query from originator %pM\n", orig_node->orig);
+}
+
+/**
+ * batadv_mcast_snoop_query_ipv6 - snoop for the selected MLD querier
+ * @skb: the unencapsulated ethernet frame coming from the mesh
+ * @orig_node: the originator this frame came from
+ *
+ * Checks whether the given frame is a general MLD query from the selected
+ * querier and if so memorizes the originator this frame came from.
+ */
+static void batadv_mcast_snoop_query_ipv6(struct sk_buff *skb,
+					  struct batadv_orig_node *orig_node)
+{
+	struct mld_msg *mld;
+	struct batadv_mcast_querier_state *querier;
+
+	if (ipv6_mc_check_mld(skb, NULL) < 0)
+		return;
+
+	mld = (struct mld_msg *)icmp6_hdr(skb);
+
+	/* we are only interested in general queries (mca == ::) */
+	if (mld->mld_type != ICMPV6_MGM_QUERY ||
+	    !ipv6_addr_any(&mld->mld_mca))
+		return;
+
+	querier = &orig_node->bat_priv->mcast.querier_ipv6;
+
+	spin_lock_bh(&querier->orig_lock);
+	rcu_assign_pointer(querier->orig, orig_node);
+	spin_unlock_bh(&querier->orig_lock);
+
+	batadv_dbg(BATADV_DBG_MCAST, orig_node->bat_priv,
+		   "Snooped MLD Query from originator %pM\n", orig_node->orig);
+}
+
+/**
+ * batadv_mcast_snoop_query - snoop the selected IGMP/MLD querier
+ * @skb: the unencapsulated ethernet frame coming from the mesh
+ * @orig_node: the originator this frame came from
+ *
+ * Checks whether the given frame is a general IGMP or MLD query
+ * from the selected querier and if so memorizes the originator
+ * this frame came from.
+ *
+ * This call might reallocate skb data.
+ */
+void batadv_mcast_snoop_query(struct sk_buff *skb,
+			      struct batadv_orig_node *orig_node)
+{
+	struct ethhdr *ethhdr = eth_hdr(skb);
+
+	switch (ntohs(ethhdr->h_proto)) {
+	case ETH_P_IP:
+		batadv_mcast_snoop_query_ipv4(skb, orig_node);
+		break;
+	case ETH_P_IPV6:
+		batadv_mcast_snoop_query_ipv6(skb, orig_node);
+		break;
+	}
+}
+
+/**
  * batadv_mcast_want_unsnoop_update - update unsnoop counter and list
  * @bat_priv: the bat priv with all the soft interface information
  * @orig: the orig_node which multicast state might have changed of
diff --git a/net/batman-adv/multicast.h b/net/batman-adv/multicast.h
index 3a44ebd..3727beb 100644
--- a/net/batman-adv/multicast.h
+++ b/net/batman-adv/multicast.h
@@ -40,6 +40,9 @@  enum batadv_forw_mode
 batadv_mcast_forw_mode(struct batadv_priv *bat_priv, struct sk_buff *skb,
 		       struct batadv_orig_node **mcast_single_orig);
 
+void batadv_mcast_snoop_query(struct sk_buff *skb,
+			      struct batadv_orig_node *orig_node);
+
 void batadv_mcast_init(struct batadv_priv *bat_priv);
 
 void batadv_mcast_free(struct batadv_priv *bat_priv);
@@ -59,6 +62,11 @@  batadv_mcast_forw_mode(struct batadv_priv *bat_priv, struct sk_buff *skb,
 	return BATADV_FORW_ALL;
 }
 
+static inline void batadv_mcast_snoop_query(struct sk_buff *skb,
+					    struct batadv_orig_node *orig_node)
+{
+}
+
 static inline int batadv_mcast_init(struct batadv_priv *bat_priv)
 {
 	return 0;
diff --git a/net/batman-adv/soft-interface.c b/net/batman-adv/soft-interface.c
index 5ec31d7..445d80e 100644
--- a/net/batman-adv/soft-interface.c
+++ b/net/batman-adv/soft-interface.c
@@ -176,6 +176,8 @@  static int batadv_interface_tx(struct sk_buff *skb,
 	if (atomic_read(&bat_priv->mesh_state) != BATADV_MESH_ACTIVE)
 		goto dropped;
 
+	skb_set_network_header(skb, ETH_HLEN);
+
 	soft_iface->trans_start = jiffies;
 	vid = batadv_get_vid(skb, 0);
 	ethhdr = eth_hdr(skb);
@@ -366,6 +368,7 @@  void batadv_interface_rx(struct net_device *soft_iface,
 
 	skb_pull_rcsum(skb, hdr_size);
 	skb_reset_mac_header(skb);
+	skb_set_network_header(skb, ETH_HLEN);
 
 	/* clean the netfilter state now that the batman-adv header has been
 	 * removed
@@ -428,6 +431,9 @@  void batadv_interface_rx(struct net_device *soft_iface,
 			skb->mark &= ~bat_priv->isolation_mark_mask;
 			skb->mark |= bat_priv->isolation_mark;
 		}
+
+		if (orig_node)
+			batadv_mcast_snoop_query(skb, orig_node);
 	} else if (batadv_is_ap_isolated(bat_priv, ethhdr->h_source,
 					 ethhdr->h_dest, vid)) {
 		goto dropped;
@@ -738,6 +744,11 @@  static int batadv_softif_init_late(struct net_device *dev)
 	atomic_set(&bat_priv->distributed_arp_table, 1);
 #endif
 #ifdef CONFIG_BATMAN_ADV_MCAST
+	rcu_assign_pointer(bat_priv->mcast.querier_ipv4.orig, NULL);
+	spin_lock_init(&bat_priv->mcast.querier_ipv4.orig_lock);
+	rcu_assign_pointer(bat_priv->mcast.querier_ipv6.orig, NULL);
+	spin_lock_init(&bat_priv->mcast.querier_ipv6.orig_lock);
+
 	bat_priv->mcast.flags = BATADV_NO_FLAGS;
 	atomic_set(&bat_priv->multicast_mode, 1);
 	atomic_set(&bat_priv->mcast.num_disabled, 0);
diff --git a/net/batman-adv/types.h b/net/batman-adv/types.h
index 9398c3f..a0f5bf8 100644
--- a/net/batman-adv/types.h
+++ b/net/batman-adv/types.h
@@ -623,12 +623,24 @@  struct batadv_priv_dat {
 
 #ifdef CONFIG_BATMAN_ADV_MCAST
 /**
+ * struct batadv_mcast_querier_state - IGMP/MLD querier state when bridged
+ * @orig: node on which the selected querier resides
+ * @orig_lock: protects updates of the selected querier in 'orig'
+ */
+struct batadv_mcast_querier_state {
+	struct batadv_orig_node __rcu *orig; /* rcu protected pointer */
+	spinlock_t orig_lock; /* protects updates of orig */
+};
+
+/**
  * struct batadv_priv_mcast - per mesh interface mcast data
  * @mla_list: list of multicast addresses we are currently announcing via TT
  * @want_all_unsnoopables_list: a list of orig_nodes wanting all unsnoopable
  *  multicast traffic
  * @want_all_ipv4_list: a list of orig_nodes wanting all IPv4 multicast traffic
  * @want_all_ipv6_list: a list of orig_nodes wanting all IPv6 multicast traffic
+ * @querier_ipv4: the current state of an IGMP querier in the mesh
+ * @querier_ipv6: the current state of an MLD querier in the mesh
  * @flags: the flags we have last sent in our mcast tvlv
  * @enabled: whether the multicast tvlv is currently enabled
  * @num_disabled: number of nodes that have no mcast tvlv
@@ -643,6 +655,8 @@  struct batadv_priv_mcast {
 	struct hlist_head want_all_unsnoopables_list;
 	struct hlist_head want_all_ipv4_list;
 	struct hlist_head want_all_ipv6_list;
+	struct batadv_mcast_querier_state querier_ipv4;
+	struct batadv_mcast_querier_state querier_ipv6;
 	uint8_t flags;
 	bool enabled;
 	atomic_t num_disabled;