From: Antonio Quartulli antonio@open-mesh.com
now that each TT entry is characterised by a VLAN ID, the latter has to be taken into consideration when computing the local/global table CRC as it would be theoretically possible to have the same client in two different VLANs
Signed-off-by: Antonio Quartulli antonio@open-mesh.com --- translation-table.c | 35 +++++++++++++++++++++++++++++++---- 1 file changed, 31 insertions(+), 4 deletions(-)
diff --git a/translation-table.c b/translation-table.c index 6c38099..761b377 100644 --- a/translation-table.c +++ b/translation-table.c @@ -1506,6 +1506,24 @@ out: * batadv_tt_global_crc - calculates the checksum of the local table belonging * to the given orig_node * @bat_priv: the bat priv with all the soft interface information + * @orig_node: originator for which the CRC should be computed + * + * This function computes the checksum for the global table corresponding to a + * particular originator. In particular the checksum is computed as follows: for + * each client connected to the originator the CRC32C of the MAC address and the + * VID is computed and then all the CRC32Cs of the various clients are xor'ed + * together. + * + * The idea behind is that CRC32C should be used as much as possible in order to + * produce a unique hash of the table, but since the order which is used to feed + * the CRC32C function affects the result and since every node in the network + * probably sorts the clients differently, the hash function cannot be directly + * computed over the entire table. Hence the CRC32C is used only on + * the single client entry, while all the results are then xor'ed together + * because the XOR operation can combine them all while trying to reduce the + * noise as much as possible. + * + * Returns the checksum of the global table of a given originator */ static uint32_t batadv_tt_global_crc(struct batadv_priv *bat_priv, struct batadv_orig_node *orig_node) @@ -1514,7 +1532,7 @@ static uint32_t batadv_tt_global_crc(struct batadv_priv *bat_priv, struct batadv_tt_common_entry *tt_common; struct batadv_tt_global_entry *tt_global; struct hlist_head *head; - uint32_t i, crc = 0; + uint32_t i, crc_tmp, crc = 0;
for (i = 0; i < hash->size; i++) { head = &hash->table[i]; @@ -1545,7 +1563,9 @@ static uint32_t batadv_tt_global_crc(struct batadv_priv *bat_priv, orig_node)) continue;
- crc ^= crc32c(0, tt_common->addr, ETH_ALEN); + crc_tmp = crc32c(0, &tt_common->vid, + sizeof(tt_common->vid)); + crc ^= crc32c(crc_tmp, tt_common->addr, ETH_ALEN); } rcu_read_unlock(); } @@ -1556,13 +1576,18 @@ static uint32_t batadv_tt_global_crc(struct batadv_priv *bat_priv, /** * batadv_tt_local_crc - calculates the checksum of the local table * @bat_priv: the bat priv with all the soft interface information + * + * For details about the computation, please refer to the documentation for + * batadv_tt_global_crc(). + * + * Returns the checksum of the local table */ static uint32_t batadv_tt_local_crc(struct batadv_priv *bat_priv) { struct batadv_hashtable *hash = bat_priv->tt.local_hash; struct batadv_tt_common_entry *tt_common; struct hlist_head *head; - uint32_t i, crc = 0; + uint32_t i, crc_tmp, crc = 0;
for (i = 0; i < hash->size; i++) { head = &hash->table[i]; @@ -1575,7 +1600,9 @@ static uint32_t batadv_tt_local_crc(struct batadv_priv *bat_priv) if (tt_common->flags & BATADV_TT_CLIENT_NEW) continue;
- crc ^= crc32c(0, tt_common->addr, ETH_ALEN); + crc_tmp = crc32c(0, &tt_common->vid, + sizeof(tt_common->vid)); + crc ^= crc32c(crc_tmp, tt_common->addr, ETH_ALEN); } rcu_read_unlock(); }