more DoS prevention: add packet_limit option to apply a hard limit to downstream...

[l2tpns.git] / l2tpns.c

diff --git a/l2tpns.c b/l2tpns.c
index f2537a4..e6d2ba4 100644 (file)
--- a/l2tpns.c
+++ b/l2tpns.c
@@ -4,7 +4,7 @@
 // Copyright (c) 2002 FireBrick (Andrews & Arnold Ltd / Watchfront Ltd) - GPL licenced
 // vim: sw=8 ts=8
 
-char const *cvs_id_l2tpns = "$Id: l2tpns.c,v 1.75 2005/01/07 07:18:33 bodea Exp $";
+char const *cvs_id_l2tpns = "$Id: l2tpns.c,v 1.76 2005/01/10 07:17:37 bodea Exp $";
 
 #include <arpa/inet.h>
 #include <assert.h>
@@ -120,6 +120,7 @@ config_descriptt config_values[] = {
        CONFIG("scheduler_fifo", scheduler_fifo, BOOL),
        CONFIG("lock_pages", lock_pages, BOOL),
        CONFIG("icmp_rate", icmp_rate, INT),
+       CONFIG("packet_limit", max_packets, INT),
        CONFIG("cluster_address", cluster_address, IPv4),
        CONFIG("cluster_interface", cluster_interface, STRING),
        CONFIG("cluster_hb_interval", cluster_hb_interval, INT),
@@ -774,7 +775,7 @@ static void processipout(uint8_t * buf, int len)
        tunnelidt t;
        in_addr_t ip;
 
-       char * data = buf;      // Keep a copy of the originals.
+       char *data = buf;       // Keep a copy of the originals.
        int size = len;
 
        uint8_t b[MAXETHER + 20];
@@ -784,13 +785,13 @@ static void processipout(uint8_t * buf, int len)
        if (len < MIN_IP_SIZE)
        {
                LOG(1, 0, 0, "Short IP, %d bytes\n", len);
-               STAT(tunnel_tx_errors);
+               STAT(tun_rx_errors);
                return;
        }
        if (len >= MAXETHER)
        {
                LOG(1, 0, 0, "Oversize IP packet %d bytes\n", len);
-               STAT(tunnel_tx_errors);
+               STAT(tun_rx_errors);
                return;
        }
 
@@ -828,6 +829,43 @@ static void processipout(uint8_t * buf, int len)
        t = session[s].tunnel;
        sp = &session[s];
 
+       // DoS prevention: enforce a maximum number of packets per 0.1s for a session
+       if (config->max_packets > 0)
+       {
+               if (sess_count[s].last_packet_out == TIME)
+               {
+                       int max = config->max_packets;
+
+                       // All packets for throttled sessions are handled by the
+                       // master, so further limit by using the throttle rate.
+                       // A bit of a kludge, since throttle rate is in kbps,
+                       // but should still be generous given our average DSL
+                       // packet size is 200 bytes: a limit of 28kbps equates
+                       // to around 180 packets per second.
+                       if (!config->cluster_iam_master && sp->throttle_out && sp->throttle_out < max)
+                               max = sp->throttle_out;
+
+                       if (++sess_count[s].packets_out > max)
+                       {
+                               sess_count[s].packets_dropped++;
+                               return;
+                       }
+               }
+               else
+               {
+                       if (sess_count[s].packets_dropped)
+                       {
+                               INC_STAT(tun_rx_dropped, sess_count[s].packets_dropped);
+                               LOG(2, s, t, "Possible DoS attack on %s (%s); dropped %u packets.",
+                                       fmtaddr(ip, 0), sp->user, sess_count[s].packets_dropped);
+                       }
+
+                       sess_count[s].last_packet_out = TIME;
+                       sess_count[s].packets_out = 1;
+                       sess_count[s].packets_dropped = 0;
+               }
+       }
+
        // run access-list if any
        if (session[s].filter_out && !ip_filter(buf, len, session[s].filter_out - 1))
                return;