Use cached session to avoid use expensive crypto_box_open_easy on every incoming session packet

Author: svpcom

src/rx.cpp

@@ -274,6 +274,7 @@ Aggregator::Aggregator(const string &keypair, uint64_t epoch, uint32_t channel_i
     last_known_block((uint64_t)-1), epoch(epoch), channel_id(channel_id)
 {
     memset(session_key, '\0', sizeof(session_key));
+    memset(session_hash, '\0', sizeof(session_hash));
 
     FILE *fp;
     if((fp = fopen(keypair.c_str(), "r")) == NULL)
@@ -571,6 +572,8 @@ void Aggregator::process_packet(const uint8_t *buf, size_t size, uint8_t wlan_id
                                 uint8_t bandwidth, sockaddr_in *sockaddr)
 {
     uint8_t session_tmp[MAX_SESSION_PACKET_SIZE - crypto_box_MACBYTES - sizeof(wsession_hdr_t)];
+    uint8_t new_session_hash[sizeof(session_hash)];
+
     wsession_data_t* new_session_data = NULL;
     //size_t new_session_tags_size = 0;
 
@@ -608,6 +611,24 @@ void Aggregator::process_packet(const uint8_t *buf, size_t size, uint8_t wlan_id
             return;
         }
 
+        if(crypto_generichash(new_session_hash,
+                              sizeof(new_session_hash),
+                              buf + sizeof(wsession_hdr_t),
+                              size - sizeof(wsession_hdr_t),
+                              ((wsession_hdr_t*)buf)->session_nonce,
+                              sizeof(((wsession_hdr_t*)buf)->session_nonce)) != 0)
+        {
+            // Should newer happened
+            assert(0);
+        }
+
+        if (memcmp(session_hash, new_session_hash, sizeof(session_hash)) == 0)
+        {
+            // Session is equal to current so we can ignore it
+            count_p_session += 1;
+            return;
+        }
+
         if(crypto_box_open_easy((uint8_t*)session_tmp,
                                 buf + sizeof(wsession_hdr_t),
                                 size - sizeof(wsession_hdr_t),
@@ -678,6 +699,9 @@ void Aggregator::process_packet(const uint8_t *buf, size_t size, uint8_t wlan_id
             IPC_MSG_SEND();
         }
 
+        // Cache already processed session
+        memcpy(session_hash, new_session_hash, sizeof(session_hash));
+
         return;
 
     default:

src/rx.hpp

@@ -221,6 +221,7 @@ class Aggregator : public BaseAggregator
     fec_t* fec_p;
     int fec_k;  // RS number of primary fragments in block
     int fec_n;  // RS total number of fragments in block
+    uint8_t session_hash[crypto_generichash_BYTES];
 
     uint32_t seq;
     rx_ring_item_t rx_ring[RX_RING_SIZE];