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Re: [PATCH 2/6] PKT_SCHED: Simple comparison ematch (cmp)

To: Thomas Graf <tgraf@xxxxxxx>
Subject: Re: [PATCH 2/6] PKT_SCHED: Simple comparison ematch (cmp)
From: Patrick McHardy <kaber@xxxxxxxxx>
Date: Mon, 24 Jan 2005 01:14:12 +0100
Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>, netdev@xxxxxxxxxxx
In-reply-to: <20050123230221.GD23931@postel.suug.ch>
References: <20050123230012.GB23931@postel.suug.ch> <20050123230221.GD23931@postel.suug.ch>
Sender: netdev-bounce@xxxxxxxxxxx
User-agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.7.5) Gecko/20050106 Debian/1.7.5-1
Thomas Graf wrote:

diff -Nru linux-2.6.11-rc2-bk1.orig/net/sched/em_cmp.c linux-2.6.11-rc2-bk1/net/sched/em_cmp.c
--- linux-2.6.11-rc2-bk1.orig/net/sched/em_cmp.c 1970-01-01 01:00:00.000000000 +0100
+++ linux-2.6.11-rc2-bk1/net/sched/em_cmp.c 2005-01-23 17:31:03.000000000 +0100
@@ -0,0 +1,101 @@
+/*
+ * net/sched/em_cmp.c Simple packet data comparison ematch
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ *
+ * Authors: Thomas Graf <tgraf@xxxxxxx>
+ */
+
+#include <linux/config.h>
+#include <linux/module.h>
+#include <linux/types.h>
+#include <linux/kernel.h>
+#include <linux/skbuff.h>
+#include <linux/tc_ematch/tc_em_cmp.h>
+#include <net/pkt_cls.h>
+
+static inline int cmp_needs_transformation(struct tcf_em_cmp *cmp)
+{
+ return unlikely(cmp->flags & TCF_EM_CMP_TRANS);
+}
+
+static int em_cmp_match(struct sk_buff *skb, struct tcf_ematch *em,
+ struct tcf_pkt_info *info)
+{
+ struct tcf_em_cmp *cmp = (struct tcf_em_cmp *) em->data;
+ unsigned char *ptr = tcf_get_base_ptr(skb, cmp->layer) + cmp->off;
+ u32 val = 0;
+
+ if (!tcf_valid_offset(skb, ptr, cmp->align))
+ return 0;
+
+ switch (cmp->align) {
+ case TCF_EM_ALIGN_U8:
+ val = *ptr;
+ break;
+
+ case TCF_EM_ALIGN_U16:
+ val = *ptr << 8;
+ val |= *(ptr+1);
+
+ if (cmp_needs_transformation(cmp))
+ val = be16_to_cpu(val);


Why not simply convert cmp->val in userspace ?

+ break;
+
+ case TCF_EM_ALIGN_U32:
+ /* Worth checking boundries? The branching seems
+ * to get worse. Visit again. */
+ val = *ptr << 24;
+ val |= *(ptr+1) << 16;
+ val |= *(ptr+2) << 8;
+ val |= *(ptr+3);
+
+ if (cmp_needs_transformation(cmp))
+ val = be32_to_cpu(val);
+ break;
+
+ default:
+ return 0;
+ }
+
+ if (cmp->mask)
+ val &= cmp->mask;
+
+ switch (cmp->opnd) {
+ case TCF_EM_OPND_EQ:
+ return val == cmp->val;
+ case TCF_EM_OPND_LT:
+ return val < cmp->val;
+ case TCF_EM_OPND_GT:
+ return val > cmp->val;
+ }
+
+ return 0;
+}
+
+static struct tcf_ematch_ops em_cmp_ops = {
+ .kind = TCF_EM_CMP,
+ .datalen = sizeof(struct tcf_em_cmp),
+ .match = em_cmp_match,
+ .owner = THIS_MODULE,
+ .link = LIST_HEAD_INIT(em_cmp_ops.link)
+};
+
+static int __init init_em_cmp(void)
+{
+ return tcf_em_register(&em_cmp_ops);
+}
+
+static void __exit exit_em_cmp(void) +{
+ tcf_em_unregister(&em_cmp_ops);
+}
+
+MODULE_LICENSE("GPL");
+
+module_init(init_em_cmp);
+module_exit(exit_em_cmp);
+






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