In case of an ARP message going in or out the soft_iface, it is intercepted and a special action is performed. In particular the DHT helper functions previously implemented are used to store all the ARP entries belonging to the network in order to provide a fast and unicast lookup instead of the classic broadcast flooding mechanism. Each node stores the entries it is responsible for (following the DHT rules) in its soft_iface ARP table. This makes it possible to reuse the kernel data structures and functions for ARP management.
Signed-off-by: Antonio Quartulli ordex@autistici.org --- distributed-arp-table.c | 226 +++++++++++++++++++++++++++++++++++++++++++++++ distributed-arp-table.h | 10 ++ main.h | 2 + send.c | 6 ++ soft-interface.c | 16 +++- 5 files changed, 259 insertions(+), 1 deletions(-)
diff --git a/distributed-arp-table.c b/distributed-arp-table.c index 6cb60b0..a1deb79 100644 --- a/distributed-arp-table.c +++ b/distributed-arp-table.c @@ -21,6 +21,8 @@
#include <linux/if_ether.h> #include <linux/if_arp.h> +/* needed to use arp_tbl */ +#include <net/arp.h>
#include "main.h" #include "distributed-arp-table.h" @@ -197,6 +199,31 @@ out: return ret; }
+/* Update the neighbour entry corresponding to the IP passed as parameter with + * the hw address hw. If the neighbour entry doesn't exists, then it will be + * created */ +static void arp_neigh_update(struct bat_priv *bat_priv, uint32_t ip, + uint8_t *hw) +{ + struct neighbour *n = NULL; + struct hard_iface *primary_if = primary_if_get_selected(bat_priv); + if (!primary_if) + goto out; + + n = __neigh_lookup(&arp_tbl, &ip, primary_if->soft_iface, 1); + if (!n) + goto out; + + bat_dbg(DBG_ARP, bat_priv, "Updating neighbour: %pI4 - %pM\n", &ip, hw); + + neigh_update(n, hw, NUD_CONNECTED, NEIGH_UPDATE_F_OVERRIDE); +out: + if (n && !IS_ERR(n)) + neigh_release(n); + if (primary_if) + hardif_free_ref(primary_if); +} + /* Returns arphdr->ar_op if the skb contains a valid ARP packet, otherwise * returns 0 */ static uint16_t arp_get_type(struct bat_priv *bat_priv, struct sk_buff *skb) @@ -239,3 +266,202 @@ static uint16_t arp_get_type(struct bat_priv *bat_priv, struct sk_buff *skb) out: return type; } + +/* return true if the message has been sent to the dht candidates, false + * otherwise. In case of true the message has to be enqueued to permit the + * fallback */ +bool arp_snoop_outgoing_request(struct bat_priv *bat_priv, struct sk_buff *skb) +{ + uint16_t type = 0; + uint32_t ip_dst, ip_src; + uint8_t *hw_src; + bool ret = false; + struct neighbour *n = NULL; + struct hard_iface *primary_if = NULL; + struct sk_buff *skb_new; + + type = arp_get_type(bat_priv, skb); + /* If we get an ARP_REQUEST we have to send the unicast message to the + * selected DHT candidates */ + if (type != ARPOP_REQUEST) + goto out; + + bat_dbg(DBG_ARP, bat_priv, "Snooped outgoing ARP request\n"); + + ip_src = ARP_IP_SRC(skb); + hw_src = ARP_HW_SRC(skb); + ip_dst = ARP_IP_DST(skb); + + primary_if = primary_if_get_selected(bat_priv); + if (!primary_if) + goto out; + + arp_neigh_update(bat_priv, ip_src, hw_src); + + n = neigh_lookup(&arp_tbl, &ip_dst, primary_if->soft_iface); + /* check if it is a valid neigh entry */ + if (n && (n->nud_state & NUD_CONNECTED)) { + skb_new = arp_create(ARPOP_REPLY, ETH_P_ARP, ip_src, + primary_if->soft_iface, ip_dst, hw_src, + n->ha, hw_src); + if (!skb_new) + goto out; + + skb_reset_mac_header(skb_new); + skb_new->protocol = eth_type_trans(skb_new, + primary_if->soft_iface); + bat_priv->stats.rx_packets++; + bat_priv->stats.rx_bytes += skb->len + sizeof(struct ethhdr); + primary_if->soft_iface->last_rx = jiffies; + + netif_rx(skb_new); + bat_dbg(DBG_ARP, bat_priv, "ARP request replied locally\n"); + } else + /* Send the request on the DHT */ + ret = dht_send_data(bat_priv, skb, ip_dst); +out: + if (n) + neigh_release(n); + if (primary_if) + hardif_free_ref(primary_if); + return ret; +} + +/* This function is meant to be invoked for an ARP request which is coming into + * the bat0 interfaces from the mesh network. It will check for the needed data + * into the local table. If found, an ARP reply is sent immediately, otherwise + * the caller has to deliver the ARP request to the upper layer */ +bool arp_snoop_incoming_request(struct bat_priv *bat_priv, struct sk_buff *skb) +{ + uint16_t type; + uint32_t ip_src, ip_dst; + uint8_t *hw_src; + struct hard_iface *primary_if = NULL; + struct sk_buff *skb_new; + struct neighbour *n = NULL; + bool ret = false; + + type = arp_get_type(bat_priv, skb); + if (type != ARPOP_REQUEST) + goto out; + + hw_src = ARP_HW_SRC(skb); + ip_src = ARP_IP_SRC(skb); + ip_dst = ARP_IP_DST(skb); + + bat_dbg(DBG_ARP, bat_priv, "Snooped incoming ARP request\n"); + + primary_if = primary_if_get_selected(bat_priv); + if (!primary_if) + goto out; + + arp_neigh_update(bat_priv, ip_src, hw_src); + + n = neigh_lookup(&arp_tbl, &ip_dst, primary_if->soft_iface); + /* check if it is a valid neigh entry */ + if (!n || !(n->nud_state & NUD_CONNECTED)) + goto out; + + skb_new = arp_create(ARPOP_REPLY, ETH_P_ARP, ip_src, + primary_if->soft_iface, ip_dst, hw_src, n->ha, + hw_src); + + if (!skb_new) + goto out; + + unicast_send_skb(skb_new, bat_priv); + + ret = true; +out: + if (n) + neigh_release(n); + if (primary_if) + hardif_free_ref(primary_if); + if (ret) + kfree_skb(skb); + return ret; +} + +/* This function is meant to be invoked on an ARP reply packet going into the + * soft interface. The related neighbour entry has to be updated and the DHT has + * to be populated as well */ +bool arp_snoop_outgoing_reply(struct bat_priv *bat_priv, struct sk_buff *skb) +{ + uint16_t type; + uint32_t ip_src, ip_dst; + uint8_t *hw_src, *hw_dst; + bool ret = false; + + type = arp_get_type(bat_priv, skb); + if (type != ARPOP_REPLY) + goto out; + + bat_dbg(DBG_ARP, bat_priv, "Snooped outgoing ARP reply\n"); + + hw_src = ARP_HW_SRC(skb); + ip_src = ARP_IP_SRC(skb); + hw_dst = ARP_HW_DST(skb); + ip_dst = ARP_IP_DST(skb); + + arp_neigh_update(bat_priv, ip_src, hw_src); + arp_neigh_update(bat_priv, ip_dst, hw_dst); + + /* Send the ARP reply to the candidates for both the IP addresses we + * fetched from the ARP reply */ + dht_send_data(bat_priv, skb, ip_src); + dht_send_data(bat_priv, skb, ip_dst); + ret = true; +out: + return ret; +} + +/* This function has to be invoked on an ARP reply coming into the soft + * interface from the mesh network. The local table has to be updated */ +bool arp_snoop_incoming_reply(struct bat_priv *bat_priv, struct sk_buff *skb) +{ + uint16_t type; + uint32_t ip_src, ip_dst; + uint8_t *hw_src, *hw_dst; + bool ret = false; + + type = arp_get_type(bat_priv, skb); + if (type != ARPOP_REPLY) + goto out; + + bat_dbg(DBG_ARP, bat_priv, "Snooped incoming ARP reply\n"); + + hw_src = ARP_HW_SRC(skb); + ip_src = ARP_IP_SRC(skb); + hw_dst = ARP_HW_DST(skb); + ip_dst = ARP_IP_DST(skb); + + /* Update our internal cache with both the IP addresses we fetched from + * the ARP reply */ + arp_neigh_update(bat_priv, ip_src, hw_src); + arp_neigh_update(bat_priv, ip_dst, hw_dst); + + ret = true; +out: + return ret; +} + +bool arp_drop_broadcast_packet(struct bat_priv *bat_priv, + struct forw_packet *forw_packet) +{ + struct neighbour *n; + + /* If this packet is an ARP_REQUEST and we already have the information + * that it is going to ask, we can drop the packet */ + if (!forw_packet->num_packets && + (arp_get_type(bat_priv, forw_packet->skb) == + ARPOP_REQUEST)) { + n = neigh_lookup(&arp_tbl, &ARP_IP_DST(forw_packet->skb), + forw_packet->if_incoming->soft_iface); + /* check if we already know this neigh */ + if (n && (n->nud_state & NUD_CONNECTED)) + return true; + + bat_dbg(DBG_ARP, bat_priv, "ARP request: fallback\n"); + } + return false; +} diff --git a/distributed-arp-table.h b/distributed-arp-table.h index 3e0f5c6..3747aad 100644 --- a/distributed-arp-table.h +++ b/distributed-arp-table.h @@ -27,6 +27,7 @@ #include <linux/if_arp.h>
struct bat_priv; +struct forw_packet;
/* * dat_addr_t is the type used for all DHT indexes. If it is changed, @@ -43,6 +44,15 @@ struct bat_priv; #define ARP_HW_DST(skb) (ARP_HW_SRC(skb) + ETH_ALEN + 4) #define ARP_IP_DST(skb) (*(uint32_t *)(ARP_HW_SRC(skb) + ETH_ALEN * 2 + 4))
+bool arp_snoop_outgoing_request(struct bat_priv *bat_priv, + struct sk_buff *skb); +bool arp_snoop_incoming_request(struct bat_priv *bat_priv, + struct sk_buff *skb); +bool arp_snoop_outgoing_reply(struct bat_priv *bat_priv, struct sk_buff *skb); +bool arp_snoop_incoming_reply(struct bat_priv *bat_priv, struct sk_buff *skb); +bool arp_drop_broadcast_packet(struct bat_priv *bat_priv, + struct forw_packet *forw_packet); + /* hash function to choose an entry in a hash table of given size */ /* hash algorithm from http://en.wikipedia.org/wiki/Hash_table */ static inline uint32_t hash_ipv4(const void *data, uint32_t size) diff --git a/main.h b/main.h index e129b01..a915db6 100644 --- a/main.h +++ b/main.h @@ -64,6 +64,8 @@
#define NULL_IFINDEX 0 /* dummy ifindex used to avoid iface checks */
+/* msecs after which an ARP_REQUEST is sent in broadcast as fallback */ +#define ARP_REQ_DELAY 250 /* numbers of originator to contact for any STORE/GET DHT operation */ #define DHT_CANDIDATES_NUM 3
diff --git a/send.c b/send.c index b00a0f5..d625998 100644 --- a/send.c +++ b/send.c @@ -20,6 +20,7 @@ */
#include "main.h" +#include "distributed-arp-table.h" #include "send.h" #include "routing.h" #include "translation-table.h" @@ -30,6 +31,8 @@ #include "originator.h" #include "bat_ogm.h"
+#include <net/arp.h> + static void send_outstanding_bcast_packet(struct work_struct *work);
/* send out an already prepared packet to the given address via the @@ -275,6 +278,9 @@ static void send_outstanding_bcast_packet(struct work_struct *work) if (atomic_read(&bat_priv->mesh_state) == MESH_DEACTIVATING) goto out;
+ if (arp_drop_broadcast_packet(bat_priv, forw_packet)) + goto out; + /* rebroadcast packet */ rcu_read_lock(); list_for_each_entry_rcu(hard_iface, &hardif_list, list) { diff --git a/soft-interface.c b/soft-interface.c index 962ee8d..21991e1 100644 --- a/soft-interface.c +++ b/soft-interface.c @@ -22,6 +22,7 @@ #include "main.h" #include "soft-interface.h" #include "hard-interface.h" +#include "distributed-arp-table.h" #include "routing.h" #include "send.h" #include "bat_debugfs.h" @@ -567,6 +568,7 @@ static int interface_tx(struct sk_buff *skb, struct net_device *soft_iface) int data_len = skb->len, ret; short vid = -1; bool do_bcast = false; + unsigned long brd_delay = 1;
if (atomic_read(&bat_priv->mesh_state) != MESH_ACTIVE) goto dropped; @@ -587,6 +589,8 @@ static int interface_tx(struct sk_buff *skb, struct net_device *soft_iface) goto end; }
+ skb_reset_mac_header(skb); + /** * if we have a another chosen mesh exit node in range * it will transport the packets to the mesh @@ -628,6 +632,9 @@ static int interface_tx(struct sk_buff *skb, struct net_device *soft_iface) if (!primary_if) goto dropped;
+ if (arp_snoop_outgoing_request(bat_priv, skb)) + brd_delay = msecs_to_jiffies(ARP_REQ_DELAY); + if (my_skb_head_push(skb, sizeof(*bcast_packet)) < 0) goto dropped;
@@ -647,7 +654,7 @@ static int interface_tx(struct sk_buff *skb, struct net_device *soft_iface) bcast_packet->seqno = htonl(atomic_inc_return(&bat_priv->bcast_seqno));
- add_bcast_packet_to_list(bat_priv, skb, 1); + add_bcast_packet_to_list(bat_priv, skb, brd_delay);
/* a copy is stored in the bcast list, therefore removing * the original skb. */ @@ -661,6 +668,8 @@ static int interface_tx(struct sk_buff *skb, struct net_device *soft_iface) goto dropped; }
+ arp_snoop_outgoing_reply(bat_priv, skb); + ret = unicast_send_skb(skb, bat_priv); if (ret != 0) goto dropped_freed; @@ -716,6 +725,11 @@ void interface_rx(struct net_device *soft_iface, goto dropped; }
+ if (arp_snoop_incoming_request(bat_priv, skb)) + goto out; + + arp_snoop_incoming_reply(bat_priv, skb); + /** * if we have a another chosen mesh exit node in range * it will transport the packets to the non-mesh network