diff -E -b -x '*o' -x '*.cmd' -x '*.mod*c' -urN include/asm/socket.h /usr/src/linux/include/asm/socket.h
--- include/asm/socket.h	2005-10-09 23:21:40.000000000 +0200
+++ /usr/src/linux/include/asm/socket.h	2005-10-11 18:31:51.000000000 +0200
@@ -53,4 +53,6 @@
 
 #define SO_PEERSEC		31
 
+#define SO_ACCEPTFILTER		32
+
 #endif /* _ASM_SOCKET_H */
diff -E -b -x '*o' -x '*.cmd' -x '*.mod*c' -urN include/net/accf.h /usr/src/linux/include/net/accf.h
--- include/net/accf.h	1970-01-01 01:00:00.000000000 +0100
+++ /usr/src/linux/include/net/accf.h	2005-10-11 20:38:52.000000000 +0200
@@ -0,0 +1,13 @@
+#ifndef _ACCF_H
+#define _ACCF_H
+
+#include <linux/config.h>
+#include <net/sock.h>
+
+extern void accf_data_handler(struct sock *sk);
+
+extern void sk_accf_install(struct sock *sk, void (*func)(struct sock *),
+    void *data);
+extern void sk_accf_uninstall(struct sock *sk);
+
+#endif
diff -E -b -x '*o' -x '*.cmd' -x '*.mod*c' -urN include/net/sock.h /usr/src/linux/include/net/sock.h
--- include/net/sock.h	2005-10-09 23:21:42.000000000 +0200
+++ /usr/src/linux/include/net/sock.h	2005-10-11 17:56:27.000000000 +0200
@@ -248,6 +248,9 @@
   	int			(*sk_backlog_rcv)(struct sock *sk,
 						  struct sk_buff *skb);  
 	void                    (*sk_destruct)(struct sock *sk);
+	void			(*sk_accf_func)(struct sock *sk);
+	void			*sk_accf_data;
+	struct sock		*sk_accf_parent;
 };
 
 /*
diff -E -b -x '*o' -x '*.cmd' -x '*.mod*c' -urN net/core/sock.c /usr/src/linux/net/core/sock.c
--- net/core/sock.c	2005-10-09 23:21:58.000000000 +0200
+++ /usr/src/linux/net/core/sock.c	2005-10-12 01:42:58.000000000 +0200
@@ -128,6 +128,8 @@
 #include <net/tcp.h>
 #endif
 
+#include <net/accf.h>
+
 /* Take into consideration the size of the struct sk_buff overhead in the
  * determination of these values, since that is non-constant across
  * platforms.  This makes socket queueing behavior and performance
@@ -440,6 +442,13 @@
 			ret = -ENONET;
 			break;
 
+		case SO_ACCEPTFILTER:
+			spin_lock_bh(&sk->sk_lock.slock);
+			/* XXX have it select the right filter */
+			sk_accf_install(sk, accf_data_handler, (void *)10);
+			spin_unlock_bh(&sk->sk_lock.slock);
+			break;
+
 		/* We implement the SO_SNDLOWAT etc to
 		   not be settable (1003.1g 5.3) */
 		default:
@@ -1118,7 +1127,9 @@
 static void sock_def_readable(struct sock *sk, int len)
 {
 	read_lock(&sk->sk_callback_lock);
-	if (sk->sk_sleep && waitqueue_active(sk->sk_sleep))
+	if (sk->sk_accf_func != NULL)
+		sk->sk_accf_func(sk);
+	else if (sk->sk_sleep && waitqueue_active(sk->sk_sleep))
 		wake_up_interruptible(sk->sk_sleep);
 	sk_wake_async(sk,1,POLL_IN);
 	read_unlock(&sk->sk_callback_lock);
diff -E -b -x '*o' -x '*.cmd' -x '*.mod*c' -urN net/ipv4/accf.c /usr/src/linux/net/ipv4/accf.c
--- net/ipv4/accf.c	1970-01-01 01:00:00.000000000 +0100
+++ /usr/src/linux/net/ipv4/accf.c	2005-10-12 01:03:20.000000000 +0200
@@ -0,0 +1,38 @@
+#include <linux/config.h>
+#include <linux/module.h>
+
+#include <net/accf.h>
+
+void accf_data_handler(struct sock *sk)
+{
+	struct sk_buff *skb;
+	int received = 0;
+	skb_queue_walk(&sk->sk_receive_queue, skb) {
+		/* XXX Should we discard certain packets? */
+		received += skb->len;
+	}
+
+	if (received >= (int)sk->sk_accf_data) {
+		printk(KERN_INFO "%s: waking up parent (%d)\n", __func__, received);
+		sk->sk_state_change(sk->sk_accf_parent);
+		sk_accf_uninstall(sk);
+	}
+}
+
+void sk_accf_install(struct sock *sk, void (*func)(struct sock *), void *data)
+{
+	sk->sk_accf_func = func;
+	sk->sk_accf_data = data;
+	sk->sk_accf_parent = sk;
+}
+
+void sk_accf_uninstall(struct sock *sk)
+{
+	sk->sk_accf_func = NULL;
+	sk->sk_accf_data = NULL;
+	sk->sk_accf_parent = NULL;
+}
+
+EXPORT_SYMBOL(accf_data_handler);
+EXPORT_SYMBOL(sk_accf_install);
+EXPORT_SYMBOL(sk_accf_uninstall);
diff -E -b -x '*o' -x '*.cmd' -x '*.mod*c' -urN net/ipv4/Makefile /usr/src/linux/net/ipv4/Makefile
--- net/ipv4/Makefile	2005-10-11 18:09:02.000000000 +0200
+++ /usr/src/linux/net/ipv4/Makefile	2005-10-11 20:02:27.000000000 +0200
@@ -7,7 +7,8 @@
 	     ip_output.o ip_sockglue.o \
 	     tcp.o tcp_input.o tcp_output.o tcp_timer.o tcp_ipv4.o tcp_minisocks.o \
 	     datagram.o raw.o udp.o arp.o icmp.o devinet.o af_inet.o igmp.o \
-	     sysctl_net_ipv4.o fib_frontend.o fib_semantics.o fib_hash.o
+	     sysctl_net_ipv4.o fib_frontend.o fib_semantics.o fib_hash.o \
+	     accf.o
 
 obj-$(CONFIG_PROC_FS) += proc.o
 obj-$(CONFIG_IP_MULTIPLE_TABLES) += fib_rules.o
diff -E -b -x '*o' -x '*.cmd' -x '*.mod*c' -urN net/ipv4/tcp_minisocks.c /usr/src/linux/net/ipv4/tcp_minisocks.c
--- net/ipv4/tcp_minisocks.c	2005-10-09 23:22:05.000000000 +0200
+++ /usr/src/linux/net/ipv4/tcp_minisocks.c	2005-10-12 01:55:52.000000000 +0200
@@ -1055,7 +1055,8 @@
 		ret = tcp_rcv_state_process(child, skb, skb->h.th, skb->len);
 
 		/* Wakeup parent, send SIGIO */
-		if (state == TCP_SYN_RECV && child->sk_state != state)
+		if (!sk->sk_accf_func &&
+		    state == TCP_SYN_RECV && child->sk_state != state)
 			parent->sk_data_ready(parent, 0);
 	} else {
 		/* Alas, it is possible again, because we do lookup