Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.

===================================================================
RCS file: /ftp/cvs/cvsroot/src/sys/netinet/ip_input.c,v
retrieving revision 1.114.4.5
retrieving revision 1.114.4.6
diff -u -p -r1.114.4.5 -r1.114.4.6
--- src/sys/netinet/ip_input.c	2001/04/06 00:24:47	1.114.4.5
+++ src/sys/netinet/ip_input.c	2001/04/24 22:21:20	1.114.4.6
@@ -1,4 +1,4 @@
-/*	$NetBSD: ip_input.c,v 1.114.4.5 2001/04/06 00:24:47 he Exp $	*/
+/*	$NetBSD: ip_input.c,v 1.114.4.6 2001/04/24 22:21:20 he Exp $	*/
 
 /*
  * Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project.
@@ -207,6 +207,8 @@ u_int16_t	ip_id;
 
 struct ipqhead ipq;
 int	ipq_locked;
+int	ip_nfragpackets = 0;
+int	ip_maxfragpackets = 200;
 
 static __inline int ipq_lock_try __P((void));
 static __inline void ipq_unlock __P((void));
@@ -759,6 +761,17 @@ ip_reass(ipqe, fp)
 	 * If first fragment to arrive, create a reassembly queue.
 	 */
 	if (fp == 0) {
+		/*
+		 * Enforce upper bound on number of fragmented packets
+		 * for which we attempt reassembly;
+		 * If maxfrag is 0, never accept fragments.
+		 * If maxfrag is -1, accept all fragments without limitation.
+		 */
+		if (ip_maxfragpackets < 0)
+			;
+		else if (ip_nfragpackets >= ip_maxfragpackets)
+			goto dropfrag;
+		ip_nfragpackets++;
 		MALLOC(fp, struct ipq *, sizeof (struct ipq),
 		    M_FTABLE, M_NOWAIT);
 		if (fp == NULL)
@@ -874,6 +887,7 @@ insert:
 	ip->ip_dst = fp->ipq_dst;
 	LIST_REMOVE(fp, ipq_q);
 	FREE(fp, M_FTABLE);
+	ip_nfragpackets--;
 	m->m_len += (ip->ip_hl << 2);
 	m->m_data -= (ip->ip_hl << 2);
 	/* some debugging cruft by sklower, below, will go away soon */
@@ -912,6 +926,7 @@ ip_freef(fp)
 	}
 	LIST_REMOVE(fp, ipq_q);
 	FREE(fp, M_FTABLE);
+	ip_nfragpackets--;
 }
 
 /*
@@ -933,6 +948,17 @@ ip_slowtimo()
 			ip_freef(fp);
 		}
 	}
+	/*
+	 * If we are over the maximum number of fragments
+	 * (due to the limit being lowered), drain off
+	 * enough to get down to the new limit.
+	 */
+	if (ip_maxfragpackets < 0)
+		;
+	else {
+		while (ip_nfragpackets > ip_maxfragpackets && ipq.lh_first)
+			ip_freef(ipq.lh_first);
+	}
 	IPQ_UNLOCK();
 #ifdef GATEWAY
 	ipflow_slowtimo();
@@ -1769,6 +1795,10 @@ ip_sysctl(name, namelen, oldp, oldlenp, 
 		return (error);
 #endif
 
+	case IPCTL_MAXFRAGPACKETS:
+		return (sysctl_int(oldp, oldlenp, newp, newlen,
+		    &ip_maxfragpackets));
+
 	default:
 		return (EOPNOTSUPP);
 	}