diff -Ndur linux-2.6.32-700/include/net/tcp.h linux-2.6.32-700-xidmask/include/net/tcp.h
--- linux-2.6.32-700/include/net/tcp.h	2013-01-10 14:18:49.880337393 -0500
+++ linux-2.6.32-700-xidmask/include/net/tcp.h	2013-01-10 14:21:16.366337329 -0500
@@ -251,6 +251,8 @@
 #ifdef CONFIG_WEB100_STATS
 extern int sysctl_web100_fperms;
 extern int sysctl_web100_gid;
+extern int sysctl_web100_sidestream_xid;
+extern int sysctl_web100_mask_xid;
 #endif
 
 extern atomic_t tcp_memory_allocated;
diff -Ndur linux-2.6.32-700/Makefile linux-2.6.32-700-xidmask/Makefile
--- linux-2.6.32-700/Makefile	2013-01-10 14:18:52.816337505 -0500
+++ linux-2.6.32-700-xidmask/Makefile	2013-01-10 14:38:46.659197193 -0500
@@ -1,7 +1,7 @@
 VERSION = 2
 PATCHLEVEL = 6
 SUBLEVEL = 32
-EXTRAVERSION = -131.tg3.220.mlab.i686
+EXTRAVERSION = .133-vs2.3.0.36.29.6.mlab.mask1.planetlab
 NAME = Man-Eating Seals of Antiquity
 RHEL_MAJOR = 6
 RHEL_MINOR = 1
diff -Ndur linux-2.6.32-700/net/ipv4/sysctl_net_ipv4.c linux-2.6.32-700-xidmask/net/ipv4/sysctl_net_ipv4.c
--- linux-2.6.32-700/net/ipv4/sysctl_net_ipv4.c	2013-01-10 14:18:50.233320698 -0500
+++ linux-2.6.32-700-xidmask/net/ipv4/sysctl_net_ipv4.c	2013-01-10 14:30:18.997403751 -0500
@@ -754,6 +754,22 @@
 		.mode		= 0644,
 		.proc_handler	= &web100_proc_dointvec_update,
 	},
+	{
+		.ctl_name	= CTL_UNNUMBERED,
+		.procname	= "web100_sidestream_xid",
+		.data		= &sysctl_web100_sidestream_xid,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= &web100_proc_dointvec_update,
+	},
+	{
+		.ctl_name	= CTL_UNNUMBERED,
+		.procname	= "web100_mask_xid",
+		.data		= &sysctl_web100_mask_xid,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= &web100_proc_dointvec_update,
+	},
 #endif
 	{
 		.ctl_name	= CTL_UNNUMBERED,
diff -Ndur linux-2.6.32-700/net/ipv4/tcp.c linux-2.6.32-700-xidmask/net/ipv4/tcp.c
--- linux-2.6.32-700/net/ipv4/tcp.c	2013-01-10 14:18:50.234322447 -0500
+++ linux-2.6.32-700-xidmask/net/ipv4/tcp.c	2013-01-10 14:21:16.368337586 -0500
@@ -297,6 +297,8 @@
 #ifdef CONFIG_WEB100_STATS
 int sysctl_web100_fperms = CONFIG_WEB100_FPERMS;
 int sysctl_web100_gid = CONFIG_WEB100_GID;
+int sysctl_web100_sidestream_xid = 0;
+int sysctl_web100_mask_xid = -1;
 #endif
 
 atomic_t tcp_memory_allocated;	/* Current allocated memory. */
@@ -848,7 +850,7 @@
 		if (copied) {
 			tcp_push(sk, flags & ~MSG_MORE, mss_now, TCP_NAGLE_PUSH);
 #ifdef CONFIG_WEB100_STATS
-			web100_update_writeq(sk);
+			WEB100_UPDATE_FUNC(tcp_sk(sk), web100_update_writeq(sk));
 #endif
 		}
 
@@ -1101,7 +1103,7 @@
 			if (copied) {
 				tcp_push(sk, flags & ~MSG_MORE, mss_now, TCP_NAGLE_PUSH);
 #ifdef CONFIG_WEB100_STATS
-				web100_update_writeq(sk);
+				WEB100_UPDATE_FUNC(tcp_sk(sk), web100_update_writeq(sk));
 #endif
 			}
 
@@ -1471,7 +1473,7 @@
 					tp->rcv_nxt, flags);
 		}
 #ifdef CONFIG_WEB100_STATS
-		web100_update_recvq(sk);
+		WEB100_UPDATE_FUNC(tcp_sk(sk), web100_update_recvq(sk));
 #endif
 
 		/* Well, if we have backlog, try to process it now yet. */
diff -Ndur linux-2.6.32-700/net/ipv4/tcp_input.c linux-2.6.32-700-xidmask/net/ipv4/tcp_input.c
--- linux-2.6.32-700/net/ipv4/tcp_input.c	2013-01-10 14:18:50.232318345 -0500
+++ linux-2.6.32-700-xidmask/net/ipv4/tcp_input.c	2013-01-10 14:21:16.371337187 -0500
@@ -3177,7 +3177,7 @@
 	}
 	
 #ifdef CONFIG_WEB100_NET100
-	if (vars->WAD_NoAI) {
+	if (stats != NULL && vars->WAD_NoAI) {
 		tp->snd_cwnd += vars->WAD_CwndAdjust;
 		vars->WAD_CwndAdjust = 0;
 		tp->snd_cwnd_stamp = tcp_time_stamp;
@@ -4426,7 +4426,7 @@
 		tcp_fast_path_check(sk);
 
 #ifdef CONFIG_WEB100_STATS
-		web100_update_recvq(sk);
+		WEB100_UPDATE_FUNC(tcp_sk(sk), web100_update_recvq(sk));
 #endif
 
 		if (eaten > 0)
@@ -4484,7 +4484,7 @@
 		   tp->rcv_nxt, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq);
 
 #ifdef CONFIG_WEB100_STATS
-	web100_update_recvq(sk);
+	WEB100_UPDATE_FUNC(tcp_sk(sk), web100_update_recvq(sk));
 #endif
 	skb_set_owner_r(skb, sk);
 
@@ -5372,7 +5372,7 @@
 			}
 
 #ifdef CONFIG_WEB100_STATS
-			web100_update_recvq(sk);
+			WEB100_UPDATE_FUNC(tcp_sk(sk), web100_update_recvq(sk));
 #endif
 			tcp_event_data_recv(sk, skb);
 
diff -Ndur linux-2.6.32-700/net/ipv4/tcp_ipv4.c linux-2.6.32-700-xidmask/net/ipv4/tcp_ipv4.c
--- linux-2.6.32-700/net/ipv4/tcp_ipv4.c	2013-01-10 14:18:50.235319018 -0500
+++ linux-2.6.32-700-xidmask/net/ipv4/tcp_ipv4.c	2013-01-10 14:21:16.372284450 -0500
@@ -1383,7 +1383,9 @@
 		sk_free(newsk);
 		goto exit;
 	}
-	tcp_sk(newsk)->tcp_stats->wc_vars.LocalAddressType = WC_ADDRTYPE_IPV4;
+	if ( tcp_sk(newsk)->tcp_stats != NULL ) {
+		tcp_sk(newsk)->tcp_stats->wc_vars.LocalAddressType = WC_ADDRTYPE_IPV4;
+	}
 #endif
 
 	newsk->sk_gso_type = SKB_GSO_TCPV4;
@@ -1857,7 +1859,9 @@
 		if ((err = web100_stats_create(sk))) {
 			return err;
 		}
-		tcp_sk(sk)->tcp_stats->wc_vars.LocalAddressType = WC_ADDRTYPE_IPV4;
+		if ( tcp_sk(sk)->tcp_stats != NULL ) {
+			tcp_sk(sk)->tcp_stats->wc_vars.LocalAddressType = WC_ADDRTYPE_IPV4;
+		}
 	}
 #endif
 
diff -Ndur linux-2.6.32-700/net/ipv4/web100_stats.c linux-2.6.32-700-xidmask/net/ipv4/web100_stats.c
--- linux-2.6.32-700/net/ipv4/web100_stats.c	2013-01-10 14:18:50.231318735 -0500
+++ linux-2.6.32-700-xidmask/net/ipv4/web100_stats.c	2013-01-10 14:21:16.373337472 -0500
@@ -252,6 +252,16 @@
 	struct web100directs *vars;
 	struct tcp_sock *tp = tcp_sk(sk);
 	struct timeval tv;
+
+	printk("Web100: stats_create(): checking xid(%d) mask(%d)\n",
+				sk->sk_xid, sysctl_web100_mask_xid);
+	if ( sk->sk_xid == sysctl_web100_mask_xid ) {
+		/* this xid is masked, so do not allocate or update tcp_stats */
+		printk("Web100: skipping stats_create() for xid(%d) mask(%d)\n",
+				sk->sk_xid, sysctl_web100_mask_xid);
+		tp->tcp_stats = NULL;
+		return 0;
+	}
 	
 	if ((stats = kmalloc(sizeof (struct web100stats), gfp_any())) == NULL)
 		return -ENOMEM;
@@ -294,6 +304,9 @@
 
 void web100_stats_destroy(struct web100stats *stats)
 {
+    if ( stats == NULL ) {
+        return;
+    }
 	/* Attribute final sndlim time. */
 	web100_update_sndlim(tcp_sk(stats->wc_sk), stats->wc_limstate);
 	
diff -Ndur linux-2.6.32-700/net/ipv6/tcp_ipv6.c linux-2.6.32-700-xidmask/net/ipv6/tcp_ipv6.c
--- linux-2.6.32-700/net/ipv6/tcp_ipv6.c	2013-01-10 14:18:50.219284269 -0500
+++ linux-2.6.32-700-xidmask/net/ipv6/tcp_ipv6.c	2013-01-10 14:21:16.373337472 -0500
@@ -1380,7 +1380,9 @@
 		sk_free(newsk);
 		goto out;
 	}
-	tcp_sk(newsk)->tcp_stats->wc_vars.LocalAddressType = WC_ADDRTYPE_IPV6;
+	if ( tcp_sk(newsk)->tcp_stats != NULL ) {
+		tcp_sk(newsk)->tcp_stats->wc_vars.LocalAddressType = WC_ADDRTYPE_IPV6;
+	}
 #endif
 
 	/*
@@ -1901,7 +1903,9 @@
 		if ((err = web100_stats_create(sk))) {
 			return err;
 		}
-		tcp_sk(sk)->tcp_stats->wc_vars.LocalAddressType = WC_ADDRTYPE_IPV6;
+		if ( tcp_sk(sk)->tcp_stats != NULL ) {
+			tcp_sk(sk)->tcp_stats->wc_vars.LocalAddressType = WC_ADDRTYPE_IPV6;
+		}
 	}
 #endif