From 68a48b6976e2bfd2f2eedc8b7ded38703bca5ebe Mon Sep 17 00:00:00 2001
From: Philippe Antoine <contact@catenacyber.fr>
Date: Fri, 8 Apr 2022 10:20:45 +0200
Subject: [PATCH] dns: store transaction in a VecDeque

instead of a simple Vector.

So that, when many old transactions get removed, suricata does not
spend much time in moving the contents of the vector, as it removes
the transaciton one by one...
---
 rust/src/dns/dns.rs | 20 +++++++++++++++-----
 1 file changed, 15 insertions(+), 5 deletions(-)

diff --git a/rust/src/dns/dns.rs b/rust/src/dns/dns.rs
index 485127e04eb1..2afe757f894f 100644
--- a/rust/src/dns/dns.rs
+++ b/rust/src/dns/dns.rs
@@ -311,7 +311,7 @@ pub struct DNSState {
     pub tx_id: u64,
 
     // Transactions.
-    pub transactions: Vec<DNSTransaction>,
+    pub transactions: VecDeque<DNSTransaction>,
 
     pub events: u16,
 
@@ -322,7 +322,8 @@ pub struct DNSState {
 
 impl State<DNSTransaction> for DNSState {
     fn get_transactions(&self) -> &[DNSTransaction] {
-        &self.transactions
+        let (r, _) = self.transactions.as_slices();
+        return r;
     }
 }
 
@@ -397,7 +398,7 @@ impl DNSState {
 
                 let mut tx = self.new_tx();
                 tx.request = Some(request);
-                self.transactions.push(tx);
+                self.transactions.push_back(tx);
 
                 if z_flag {
                     SCLogDebug!("Z-flag set on DNS response");
@@ -441,7 +442,7 @@ impl DNSState {
                     }
                 }
                 tx.response = Some(response);
-                self.transactions.push(tx);
+                self.transactions.push_back(tx);
 
                 if z_flag {
                     SCLogDebug!("Z-flag set on DNS response");
@@ -926,6 +927,15 @@ pub unsafe extern "C" fn rs_dns_apply_tx_config(
     }
 }
 
+pub unsafe extern "C" fn rs_dns_get_tx_iterator<S: State<Tx>, Tx: Transaction>(
+    _ipproto: u8, _alproto: AppProto, state: *mut std::os::raw::c_void, min_tx_id: u64,
+    _max_tx_id: u64, istate: &mut u64,
+) -> AppLayerGetTxIterTuple {
+    let state = cast_pointer!(state, DNSState);
+    state.transactions.make_contiguous();
+    state.get_transaction_iterator(min_tx_id, istate)
+}
+
 #[no_mangle]
 pub unsafe extern "C" fn rs_dns_udp_register_parser() {
     let default_port = std::ffi::CString::new("[53]").unwrap();
@@ -952,7 +962,7 @@ pub unsafe extern "C" fn rs_dns_udp_register_parser() {
         localstorage_new: None,
         localstorage_free: None,
         get_files: None,
-        get_tx_iterator: Some(crate::applayer::state_get_tx_iterator::<DNSState, DNSTransaction>),
+        get_tx_iterator: Some(rs_dns_get_tx_iterator::<DNSState, DNSTransaction>),
         get_tx_data: rs_dns_state_get_tx_data,
         apply_tx_config: Some(rs_dns_apply_tx_config),
         flags: APP_LAYER_PARSER_OPT_UNIDIR_TXS,