bonding: delete migrated IP addresses from the rlb hash table

Bonding in balance-alb mode records information from ARP packets
passing through the bond in a hash table (rx_hashtbl).

At certain situations (e.g. link change of a slave),
rlb_update_rx_clients() will send out ARP packets to update ARP
caches of other hosts on the network to achieve RX load
balancing.

The problem is that once an IP address is recorded in the hash
table, it stays there indefinitely. If this IP address is
migrated to a different host in the network, bonding still sends
out ARP packets that poison other systems' ARP caches with
invalid information.

This patch solves this by looking at all incoming ARP packets,
and checking if the source IP address is one of the source
addresses stored in the rx_hashtbl. If it is, but the MAC
addresses differ, the corresponding hash table entries are
removed. Thus, when an IP address is migrated, the first ARP
broadcast by its new owner will purge the offending entries of
rx_hashtbl.

The hash table is hashed by ip_dst. To be able to do the above
check efficiently (not walking the whole hash table), we need a
reverse mapping (by ip_src).

I added three new members in struct rlb_client_info:
   rx_hashtbl[x].src_first will point to the start of a list of
      entries for which hash(ip_src) == x.
   The list is linked with src_next and src_prev.

When an incoming ARP packet arrives at rlb_arp_recv()
rlb_purge_src_ip() can quickly walk only the entries on the
corresponding lists, i.e. the entries that are likely to contain
the offending IP address.

To avoid confusion, I renamed these existing fields of struct
rlb_client_info:
	next -> used_next
	prev -> used_prev
	rx_hashtbl_head -> rx_hashtbl_used_head

(The current linked list is _not_ a list of hash table
entries with colliding ip_dst. It's a list of entries that are
being used; its purpose is to avoid walking the whole hash table
when looking for used entries.)

Signed-off-by: Jiri Bohac <jbohac@suse.cz>
Signed-off-by: Jay Vosburgh <fubar@us.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 157 insertions, 34 deletions

diff --git a/drivers/net/bonding/bond_alb.c b/drivers/net/bonding/bond_alb.c
index 6fecb52..7c9d136 100644
--- a/drivers/net/bonding/bond_alb.c
+++ b/drivers/net/bonding/bond_alb.c
@@ -84,6 +84,10 @@ static inline struct arp_pkt *arp_pkt(const struct sk_buff *skb)
 
 /* Forward declaration */
 static void alb_send_learning_packets(struct slave *slave, u8 mac_addr[]);
+static void rlb_purge_src_ip(struct bonding *bond, struct arp_pkt *arp);
+static void rlb_src_unlink(struct bonding *bond, u32 index);
+static void rlb_src_link(struct bonding *bond, u32 ip_src_hash,
+			 u32 ip_dst_hash);
 
 static inline u8 _simple_hash(const u8 *hash_start, int hash_size)
 {
@@ -354,6 +358,18 @@ static int rlb_arp_recv(const struct sk_buff *skb, struct bonding *bond,
 	if (!arp)
 		goto out;
 
+	/* We received an ARP from arp->ip_src.
+	 * We might have used this IP address previously (on the bonding host
+	 * itself or on a system that is bridged together with the bond).
+	 * However, if arp->mac_src is different than what is stored in
+	 * rx_hashtbl, some other host is now using the IP and we must prevent
+	 * sending out client updates with this IP address and the old MAC
+	 * address.
+	 * Clean up all hash table entries that have this address as ip_src but
+	 * have a different mac_src.
+	 */
+	rlb_purge_src_ip(bond, arp);
+
 	if (arp->op_code == htons(ARPOP_REPLY)) {
 		/* update rx hash table for this ARP */
 		rlb_update_entry_from_arp(bond, arp);
@@ -432,9 +448,9 @@ static void rlb_clear_slave(struct bonding *bond, struct slave *slave)
 	_lock_rx_hashtbl_bh(bond);
 
 	rx_hash_table = bond_info->rx_hashtbl;
-	index = bond_info->rx_hashtbl_head;
+	index = bond_info->rx_hashtbl_used_head;
 	for (; index != RLB_NULL_INDEX; index = next_index) {
-		next_index = rx_hash_table[index].next;
+		next_index = rx_hash_table[index].used_next;
 		if (rx_hash_table[index].slave == slave) {
 			struct slave *assigned_slave = rlb_next_rx_slave(bond);
 
@@ -519,8 +535,9 @@ static void rlb_update_rx_clients(struct bonding *bond)
 
 	_lock_rx_hashtbl_bh(bond);
 
-	hash_index = bond_info->rx_hashtbl_head;
-	for (; hash_index != RLB_NULL_INDEX; hash_index = client_info->next) {
+	hash_index = bond_info->rx_hashtbl_used_head;
+	for (; hash_index != RLB_NULL_INDEX;
+	     hash_index = client_info->used_next) {
 		client_info = &(bond_info->rx_hashtbl[hash_index]);
 		if (client_info->ntt) {
 			rlb_update_client(client_info);
@@ -548,8 +565,9 @@ static void rlb_req_update_slave_clients(struct bonding *bond, struct slave *sla
 
 	_lock_rx_hashtbl_bh(bond);
 
-	hash_index = bond_info->rx_hashtbl_head;
-	for (; hash_index != RLB_NULL_INDEX; hash_index = client_info->next) {
+	hash_index = bond_info->rx_hashtbl_used_head;
+	for (; hash_index != RLB_NULL_INDEX;
+	     hash_index = client_info->used_next) {
 		client_info = &(bond_info->rx_hashtbl[hash_index]);
 
 		if ((client_info->slave == slave) &&
@@ -578,8 +596,9 @@ static void rlb_req_update_subnet_clients(struct bonding *bond, __be32 src_ip)
 
 	_lock_rx_hashtbl(bond);
 
-	hash_index = bond_info->rx_hashtbl_head;
-	for (; hash_index != RLB_NULL_INDEX; hash_index = client_info->next) {
+	hash_index = bond_info->rx_hashtbl_used_head;
+	for (; hash_index != RLB_NULL_INDEX;
+	     hash_index = client_info->used_next) {
 		client_info = &(bond_info->rx_hashtbl[hash_index]);
 
 		if (!client_info->slave) {
@@ -625,6 +644,7 @@ static struct slave *rlb_choose_channel(struct sk_buff *skb, struct bonding *bon
 				/* update mac address from arp */
 				memcpy(client_info->mac_dst, arp->mac_dst, ETH_ALEN);
 			}
+			memcpy(client_info->mac_src, arp->mac_src, ETH_ALEN);
 
 			assigned_slave = client_info->slave;
 			if (assigned_slave) {
@@ -647,6 +667,17 @@ static struct slave *rlb_choose_channel(struct sk_buff *skb, struct bonding *bon
 	assigned_slave = rlb_next_rx_slave(bond);
 
 	if (assigned_slave) {
+		if (!(client_info->assigned &&
+		      client_info->ip_src == arp->ip_src)) {
+			/* ip_src is going to be updated,
+			 * fix the src hash list
+			 */
+			u32 hash_src = _simple_hash((u8 *)&arp->ip_src,
+						    sizeof(arp->ip_src));
+			rlb_src_unlink(bond, hash_index);
+			rlb_src_link(bond, hash_src, hash_index);
+		}
+
 		client_info->ip_src = arp->ip_src;
 		client_info->ip_dst = arp->ip_dst;
 		/* arp->mac_dst is broadcast for arp reqeusts.
@@ -654,6 +685,7 @@ static struct slave *rlb_choose_channel(struct sk_buff *skb, struct bonding *bon
 		 * upon receiving an arp reply.
 		 */
 		memcpy(client_info->mac_dst, arp->mac_dst, ETH_ALEN);
+		memcpy(client_info->mac_src, arp->mac_src, ETH_ALEN);
 		client_info->slave = assigned_slave;
 
 		if (!ether_addr_equal_64bits(client_info->mac_dst, mac_bcast)) {
@@ -669,11 +701,11 @@ static struct slave *rlb_choose_channel(struct sk_buff *skb, struct bonding *bon
 		}
 
 		if (!client_info->assigned) {
-			u32 prev_tbl_head = bond_info->rx_hashtbl_head;
-			bond_info->rx_hashtbl_head = hash_index;
-			client_info->next = prev_tbl_head;
+			u32 prev_tbl_head = bond_info->rx_hashtbl_used_head;
+			bond_info->rx_hashtbl_used_head = hash_index;
+			client_info->used_next = prev_tbl_head;
 			if (prev_tbl_head != RLB_NULL_INDEX) {
-				bond_info->rx_hashtbl[prev_tbl_head].prev =
+				bond_info->rx_hashtbl[prev_tbl_head].used_prev =
 					hash_index;
 			}
 			client_info->assigned = 1;
@@ -746,8 +778,9 @@ static void rlb_rebalance(struct bonding *bond)
 	_lock_rx_hashtbl_bh(bond);
 
 	ntt = 0;
-	hash_index = bond_info->rx_hashtbl_head;
-	for (; hash_index != RLB_NULL_INDEX; hash_index = client_info->next) {
+	hash_index = bond_info->rx_hashtbl_used_head;
+	for (; hash_index != RLB_NULL_INDEX;
+	     hash_index = client_info->used_next) {
 		client_info = &(bond_info->rx_hashtbl[hash_index]);
 		assigned_slave = rlb_next_rx_slave(bond);
 		if (assigned_slave && (client_info->slave != assigned_slave)) {
@@ -765,11 +798,113 @@ static void rlb_rebalance(struct bonding *bond)
 }
 
 /* Caller must hold rx_hashtbl lock */
+static void rlb_init_table_entry_dst(struct rlb_client_info *entry)
+{
+	entry->used_next = RLB_NULL_INDEX;
+	entry->used_prev = RLB_NULL_INDEX;
+	entry->assigned = 0;
+	entry->slave = NULL;
+	entry->tag = 0;
+}
+static void rlb_init_table_entry_src(struct rlb_client_info *entry)
+{
+	entry->src_first = RLB_NULL_INDEX;
+	entry->src_prev = RLB_NULL_INDEX;
+	entry->src_next = RLB_NULL_INDEX;
+}
+
 static void rlb_init_table_entry(struct rlb_client_info *entry)
 {
 	memset(entry, 0, sizeof(struct rlb_client_info));
-	entry->next = RLB_NULL_INDEX;
-	entry->prev = RLB_NULL_INDEX;
+	rlb_init_table_entry_dst(entry);
+	rlb_init_table_entry_src(entry);
+}
+
+static void rlb_delete_table_entry_dst(struct bonding *bond, u32 index)
+{
+	struct alb_bond_info *bond_info = &(BOND_ALB_INFO(bond));
+	u32 next_index = bond_info->rx_hashtbl[index].used_next;
+	u32 prev_index = bond_info->rx_hashtbl[index].used_prev;
+
+	if (index == bond_info->rx_hashtbl_used_head)
+		bond_info->rx_hashtbl_used_head = next_index;
+	if (prev_index != RLB_NULL_INDEX)
+		bond_info->rx_hashtbl[prev_index].used_next = next_index;
+	if (next_index != RLB_NULL_INDEX)
+		bond_info->rx_hashtbl[next_index].used_prev = prev_index;
+}
+
+/* unlink a rlb hash table entry from the src list */
+static void rlb_src_unlink(struct bonding *bond, u32 index)
+{
+	struct alb_bond_info *bond_info = &(BOND_ALB_INFO(bond));
+	u32 next_index = bond_info->rx_hashtbl[index].src_next;
+	u32 prev_index = bond_info->rx_hashtbl[index].src_prev;
+
+	bond_info->rx_hashtbl[index].src_next = RLB_NULL_INDEX;
+	bond_info->rx_hashtbl[index].src_prev = RLB_NULL_INDEX;
+
+	if (next_index != RLB_NULL_INDEX)
+		bond_info->rx_hashtbl[next_index].src_prev = prev_index;
+
+	if (prev_index == RLB_NULL_INDEX)
+		return;
+
+	/* is prev_index pointing to the head of this list? */
+	if (bond_info->rx_hashtbl[prev_index].src_first == index)
+		bond_info->rx_hashtbl[prev_index].src_first = next_index;
+	else
+		bond_info->rx_hashtbl[prev_index].src_next = next_index;
+
+}
+
+static void rlb_delete_table_entry(struct bonding *bond, u32 index)
+{
+	struct alb_bond_info *bond_info = &(BOND_ALB_INFO(bond));
+	struct rlb_client_info *entry = &(bond_info->rx_hashtbl[index]);
+
+	rlb_delete_table_entry_dst(bond, index);
+	rlb_init_table_entry_dst(entry);
+
+	rlb_src_unlink(bond, index);
+}
+
+/* add the rx_hashtbl[ip_dst_hash] entry to the list
+ * of entries with identical ip_src_hash
+ */
+static void rlb_src_link(struct bonding *bond, u32 ip_src_hash, u32 ip_dst_hash)
+{
+	struct alb_bond_info *bond_info = &(BOND_ALB_INFO(bond));
+	u32 next;
+
+	bond_info->rx_hashtbl[ip_dst_hash].src_prev = ip_src_hash;
+	next = bond_info->rx_hashtbl[ip_src_hash].src_first;
+	bond_info->rx_hashtbl[ip_dst_hash].src_next = next;
+	if (next != RLB_NULL_INDEX)
+		bond_info->rx_hashtbl[next].src_prev = ip_dst_hash;
+	bond_info->rx_hashtbl[ip_src_hash].src_first = ip_dst_hash;
+}
+
+/* deletes all rx_hashtbl entries with  arp->ip_src if their mac_src does
+ * not match arp->mac_src */
+static void rlb_purge_src_ip(struct bonding *bond, struct arp_pkt *arp)
+{
+	struct alb_bond_info *bond_info = &(BOND_ALB_INFO(bond));
+	u32 ip_src_hash = _simple_hash((u8*)&(arp->ip_src), sizeof(arp->ip_src));
+	u32 index;
+
+	_lock_rx_hashtbl_bh(bond);
+
+	index = bond_info->rx_hashtbl[ip_src_hash].src_first;
+	while (index != RLB_NULL_INDEX) {
+		struct rlb_client_info *entry = &(bond_info->rx_hashtbl[index]);
+		u32 next_index = entry->src_next;
+		if (entry->ip_src == arp->ip_src &&
+		    !ether_addr_equal_64bits(arp->mac_src, entry->mac_src))
+				rlb_delete_table_entry(bond, index);
+		index = next_index;
+	}
+	_unlock_rx_hashtbl_bh(bond);
 }
 
 static int rlb_initialize(struct bonding *bond)
@@ -787,7 +922,7 @@ static int rlb_initialize(struct bonding *bond)
 
 	bond_info->rx_hashtbl = new_hashtbl;
 
-	bond_info->rx_hashtbl_head = RLB_NULL_INDEX;
+	bond_info->rx_hashtbl_used_head = RLB_NULL_INDEX;
 
 	for (i = 0; i < RLB_HASH_TABLE_SIZE; i++) {
 		rlb_init_table_entry(bond_info->rx_hashtbl + i);
@@ -809,7 +944,7 @@ static void rlb_deinitialize(struct bonding *bond)
 
 	kfree(bond_info->rx_hashtbl);
 	bond_info->rx_hashtbl = NULL;
-	bond_info->rx_hashtbl_head = RLB_NULL_INDEX;
+	bond_info->rx_hashtbl_used_head = RLB_NULL_INDEX;
 
 	_unlock_rx_hashtbl_bh(bond);
 }
@@ -821,25 +956,13 @@ static void rlb_clear_vlan(struct bonding *bond, unsigned short vlan_id)
 
 	_lock_rx_hashtbl_bh(bond);
 
-	curr_index = bond_info->rx_hashtbl_head;
+	curr_index = bond_info->rx_hashtbl_used_head;
 	while (curr_index != RLB_NULL_INDEX) {
 		struct rlb_client_info *curr = &(bond_info->rx_hashtbl[curr_index]);
-		u32 next_index = bond_info->rx_hashtbl[curr_index].next;
-		u32 prev_index = bond_info->rx_hashtbl[curr_index].prev;
-
-		if (curr->tag && (curr->vlan_id == vlan_id)) {
-			if (curr_index == bond_info->rx_hashtbl_head) {
-				bond_info->rx_hashtbl_head = next_index;
-			}
-			if (prev_index != RLB_NULL_INDEX) {
-				bond_info->rx_hashtbl[prev_index].next = next_index;
-			}
-			if (next_index != RLB_NULL_INDEX) {
-				bond_info->rx_hashtbl[next_index].prev = prev_index;
-			}
+		u32 next_index = bond_info->rx_hashtbl[curr_index].used_next;
 
-			rlb_init_table_entry(curr);
-		}
+		if (curr->tag && (curr->vlan_id == vlan_id))
+			rlb_delete_table_entry(bond, curr_index);
 
 		curr_index = next_index;
 	}