nfs: implement post-GAP transaction cleanup

Close all prior transactions in the direction of the GAP, except the
file xfers. Those use their own logic described below.

After a GAP all normal transactions are closed. File transactions
are left open as they can handle GAPs in principle. However, the
GAP might have contained the closing of a file and therefore it
may remain active until the end of the flow.

This patch introduces a time based heuristic for these transactions.
After the GAP all file transactions are stamped with the current
timestamp. If 60 seconds later a file has seen no update, its marked
as closed.

This is meant to fix resource starvation issues observed in long
running SMB sessions where packet loss was causing GAPs. Due to the
similarity of the NFS and SMB parsers, this issue is fixed for NFS
as well in this patch.

Bug #3424.
Bug #3425.

rust/src/nfs/nfs.rs

@@ -119,6 +119,10 @@ pub struct NFSTransactionFile {
     /// last xid of this file transfer. Last READ or COMMIT normally.
     pub file_last_xid: u32,
 
+    /// after a gap, this will be set to a time in the future. If the file
+    /// receives no updates before that, it will be considered complete.
+    pub post_gap_ts: u64,
+
     /// file tracker for a single file. Boxed so that we don't use
     /// as much space if we're not a file tx.
     pub file_tracker: FileTransferTracker,
@@ -130,6 +134,7 @@ impl NFSTransactionFile {
             file_additional_procs: Vec::new(),
             chunk_count:0,
             file_last_xid: 0,
+            post_gap_ts: 0,
             file_tracker: FileTransferTracker::new(),
         }
     }
@@ -338,12 +343,20 @@ pub struct NFSState {
 
     is_udp: bool,
 
+    /// true as long as we have file txs that are in a post-gap
+    /// state. It means we'll do extra house keeping for those.
+    check_post_gap_file_txs: bool,
+
     pub nfs_version: u16,
 
     pub events: u16,
 
     /// tx counter for assigning incrementing id's to tx's
     tx_id: u64,
+
+    /// Timestamp in seconds of last update. This is packet time,
+    /// potentially coming from pcaps.
+    ts: u64,
 }
 
 impl NFSState {
@@ -366,9 +379,11 @@ impl NFSState {
             ts_gap:false,
             tc_gap:false,
             is_udp:false,
+            check_post_gap_file_txs:false,
             nfs_version:0,
             events:0,
             tx_id:0,
+            ts: 0,
         }
     }
     pub fn free(&mut self) {
@@ -483,6 +498,71 @@ impl NFSState {
         }
     }
 
+    fn post_gap_housekeeping_for_files(&mut self)
+    {
+        let mut post_gap_txs = false;
+        for tx in &mut self.transactions {
+            if let Some(NFSTransactionTypeData::FILE(ref f)) = tx.type_data {
+                if f.post_gap_ts > 0 {
+                    if self.ts > f.post_gap_ts {
+                        tx.request_done = true;
+                        tx.response_done = true;
+                    } else {
+                        post_gap_txs = true;
+                    }
+                }
+            }
+        }
+        self.check_post_gap_file_txs = post_gap_txs;
+    }
+
+    /* after a gap we will consider all transactions complete for our
+     * direction. File transfer transactions are an exception. Those
+     * can handle gaps. For the file transactions we set the current
+     * (flow) time and prune them in 60 seconds if no update for them
+     * was received. */
+    fn post_gap_housekeeping(&mut self, dir: u8)
+    {
+        if self.ts_ssn_gap && dir == STREAM_TOSERVER {
+            for tx in &mut self.transactions {
+                if tx.id >= self.tx_id {
+                    SCLogDebug!("post_gap_housekeeping: done");
+                    break;
+                }
+                if let Some(NFSTransactionTypeData::FILE(ref mut f)) = tx.type_data {
+                    // leaving FILE txs open as they can deal with gaps. We
+                    // remove them after 60 seconds of no activity though.
+                    if f.post_gap_ts == 0 {
+                        f.post_gap_ts = self.ts + 60;
+                        self.check_post_gap_file_txs = true;
+                    }
+                } else {
+                    SCLogDebug!("post_gap_housekeeping: tx {} marked as done TS", tx.id);
+                    tx.request_done = true;
+                }
+            }
+        } else if self.tc_ssn_gap && dir == STREAM_TOCLIENT {
+            for tx in &mut self.transactions {
+                if tx.id >= self.tx_id {
+                    SCLogDebug!("post_gap_housekeeping: done");
+                    break;
+                }
+                if let Some(NFSTransactionTypeData::FILE(ref mut f)) = tx.type_data {
+                    // leaving FILE txs open as they can deal with gaps. We
+                    // remove them after 60 seconds of no activity though.
+                    if f.post_gap_ts == 0 {
+                        f.post_gap_ts = self.ts + 60;
+                        self.check_post_gap_file_txs = true;
+                    }
+                } else {
+                    SCLogDebug!("post_gap_housekeeping: tx {} marked as done TC", tx.id);
+                    tx.request_done = true;
+                    tx.response_done = true;
+                }
+            }
+        }
+    }
+
     pub fn process_request_record_lookup<'b>(&mut self, r: &RpcPacket<'b>, xidmap: &mut NFSRequestXidMap) {
         match parse_nfs3_request_lookup(r.prog_data) {
             Ok((_, lookup)) => {
@@ -764,6 +844,11 @@ impl NFSState {
                         }
                     }
 
+                    // reset timestamp if we get called after a gap
+                    if tdf.post_gap_ts > 0 {
+                        tdf.post_gap_ts = 0;
+                    }
+
                     tdf.chunk_count += 1;
                     let cs = tdf.file_tracker.update(files, flags, data, gap_size);
                     /* see if we need to close the tx */
@@ -1113,6 +1198,12 @@ impl NFSState {
                 },
             }
         };
+
+        self.post_gap_housekeeping(STREAM_TOSERVER);
+        if self.check_post_gap_file_txs {
+            self.post_gap_housekeeping_for_files();
+        }
+
         status
     }
 
@@ -1271,6 +1362,10 @@ impl NFSState {
                 },
             }
         };
+        self.post_gap_housekeeping(STREAM_TOCLIENT);
+        if self.check_post_gap_file_txs {
+            self.post_gap_housekeeping_for_files();
+        }
         status
     }
     /// Parsing function
@@ -1357,7 +1452,7 @@ pub extern "C" fn rs_nfs_state_free(state: *mut std::os::raw::c_void) {
 
 /// C binding parse a NFS TCP request. Returns 1 on success, -1 on failure.
 #[no_mangle]
-pub extern "C" fn rs_nfs_parse_request(_flow: *mut Flow,
+pub extern "C" fn rs_nfs_parse_request(flow: &mut Flow,
                                        state: &mut NFSState,
                                        _pstate: *mut std::os::raw::c_void,
                                        input: *const u8,
@@ -1368,6 +1463,7 @@ pub extern "C" fn rs_nfs_parse_request(_flow: *mut Flow,
     let buf = unsafe{std::slice::from_raw_parts(input, input_len as usize)};
     SCLogDebug!("parsing {} bytes of request data", input_len);
 
+    state.ts = flow.get_last_time().as_secs();
     if state.parse_tcp_data_ts(buf) == 0 {
         1
     } else {
@@ -1388,7 +1484,7 @@ pub extern "C" fn rs_nfs_parse_request_tcp_gap(
 }
 
 #[no_mangle]
-pub extern "C" fn rs_nfs_parse_response(_flow: *mut Flow,
+pub extern "C" fn rs_nfs_parse_response(flow: &mut Flow,
                                         state: &mut NFSState,
                                         _pstate: *mut std::os::raw::c_void,
                                         input: *const u8,
@@ -1399,6 +1495,7 @@ pub extern "C" fn rs_nfs_parse_response(_flow: *mut Flow,
     SCLogDebug!("parsing {} bytes of response data", input_len);
     let buf = unsafe{std::slice::from_raw_parts(input, input_len as usize)};
 
+    state.ts = flow.get_last_time().as_secs();
     if state.parse_tcp_data_tc(buf) == 0 {
         1
     } else {