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Date: Thu, 27 Jan 2000 09:12:47 -0700
From: John Watkins <jwatkin@hungry.com.>
To: [email protected]
Subject: Multicast from hell

 Here is a patch for FreeBSD

--- tcp_input.c.orig    Tue Apr 20 15:09:15 1999
+ tcp_input.c Fri Jan 21 21:53:00 2000
@@ -398,12 +398,36 @@
                            "Connection attempt to TCP %s:%d from
%s:%d\n",
                            buf, ntohs(ti->ti_dport),
inet_ntoa(ti->ti_src),
                            ntohs(ti->ti_sport));
-               }
+               } else if (tiflags & TH_ACK) {
+                       /*
+                        * Alpha code in response to stream.c
+                        * - Omachonu Ogali
+                        */
+                       char buf[4*sizeof "123"];
+
+#ifdef ICMP_BANDLIM
+                       if (badport_bandlim(1) < 0)
+                               goto drop;
+#endif
+
+                       strcpy(buf, inet_ntoa(ti->ti_dst));
+                       log(LOG_INFO,
+                           "received TCP/ACK to non existant
connection: %s:%d -> %s:%d\n",
+                           inet_ntoa(ti->ti_src), ntohs(ti->ti_sport),
buf,
ntohs(ti->ti_dport));
+
+                       /*
+                        * Drop without reset to prevent smurf-like tcp
+                        * attack
+                        */
+
+                       goto drop;
+               } else {
 #ifdef ICMP_BANDLIM
                if (badport_bandlim(1) < 0)
                        goto drop;
 #endif
                goto dropwithreset;
+               }
        }
        tp = intotcpcb(inp);
        if (tp == 0)

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