From 0b4d50d7bddc70b289cfda422f65e33e05406a18 Mon Sep 17 00:00:00 2001
From: yamt <yamt@NetBSD.org>
Date: Thu, 7 Apr 2005 12:22:47 +0000
Subject: [PATCH] when doing TSO, avoid to use duplicated ip_id heavily. XXX
 ip_randomid

---
 sys/netinet/ip_output.c | 25 ++++++++++++++++++++++---
 sys/netinet/ip_var.h    | 28 ++++++++++++++++++++++++----
 2 files changed, 46 insertions(+), 7 deletions(-)

diff --git a/sys/netinet/ip_output.c b/sys/netinet/ip_output.c
index 9993af1f5f05..2520169b4880 100644
--- a/sys/netinet/ip_output.c
+++ b/sys/netinet/ip_output.c
@@ -1,4 +1,4 @@
-/*	$NetBSD: ip_output.c,v 1.149 2005/03/11 17:07:51 matt Exp $	*/
+/*	$NetBSD: ip_output.c,v 1.150 2005/04/07 12:22:47 yamt Exp $	*/
 
 /*
  * Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project.
@@ -98,7 +98,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: ip_output.c,v 1.149 2005/03/11 17:07:51 matt Exp $");
+__KERNEL_RCSID(0, "$NetBSD: ip_output.c,v 1.150 2005/04/07 12:22:47 yamt Exp $");
 
 #include "opt_pfil_hooks.h"
 #include "opt_inet.h"
@@ -235,7 +235,26 @@ ip_output(struct mbuf *m0, ...)
 	if ((flags & (IP_FORWARDING|IP_RAWOUTPUT)) == 0) {
 		ip->ip_v = IPVERSION;
 		ip->ip_off = htons(0);
-		ip->ip_id = ip_newid();
+		if ((m->m_pkthdr.csum_flags & M_CSUM_TSOv4) == 0) {
+			ip->ip_id = ip_newid();
+		} else {
+
+			/*
+			 * TSO capable interfaces (typically?) increment
+			 * ip_id for each segment.
+			 * "allocate" enough ids here to increase the chance
+			 * for them to be unique.
+			 *
+			 * note that the following calculation is not
+			 * needed to be precise.  wasting some ip_id is fine.
+			 */
+
+			unsigned int segsz = m->m_pkthdr.segsz;
+			unsigned int datasz = ntohs(ip->ip_len) - hlen;
+			unsigned int num = howmany(datasz, segsz);
+
+			ip->ip_id = ip_newid_range(num);
+		}
 		ip->ip_hl = hlen >> 2;
 		ipstat.ips_localout++;
 	} else {
diff --git a/sys/netinet/ip_var.h b/sys/netinet/ip_var.h
index e4729fb2ffed..bad2961ce120 100644
--- a/sys/netinet/ip_var.h
+++ b/sys/netinet/ip_var.h
@@ -1,4 +1,4 @@
-/*	$NetBSD: ip_var.h,v 1.69 2004/12/15 04:25:19 thorpej Exp $	*/
+/*	$NetBSD: ip_var.h,v 1.70 2005/04/07 12:22:47 yamt Exp $	*/
 
 /*
  * Copyright (c) 1982, 1986, 1993
@@ -263,13 +263,33 @@ static __inline uint16_t ip_newid(void);
 u_int16_t ip_randomid(void);
 extern int ip_do_randomid;
 
+/*
+ * ip_newid_range: "allocate" num contiguous ip_ids.
+ *
+ * => return the first id.
+ */
+
+static __inline uint16_t
+ip_newid_range(unsigned int num)
+{
+	uint16_t id;
+
+	if (ip_do_randomid) {
+		/* XXX ignore num */
+		return ip_randomid();
+	}
+
+	id = htons(ip_id);
+	ip_id += num;
+
+	return id;
+}
+
 static __inline uint16_t
 ip_newid(void)
 {
-	if (ip_do_randomid)
-		return ip_randomid();
 
-	return htons(ip_id++);
+	return ip_newid_range(1);
 }
 
 #endif  /* _KERNEL */