netdev - [PATCH net-next] net:sched: add action inheritdsfield to skbmod

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Message-ID: <2F042100-2BAC-48E5-887C-5D426B1D5A5B@bu.edu>
Date:   Thu, 17 May 2018 19:33:08 +0000
From:   "Fu, Qiaobin" <qiaobinf@...edu>
To:     "davem@...emloft.net" <davem@...emloft.net>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "jhs@...atatu.com" <jhs@...atatu.com>,
        Michel Machado <michel@...irati.com.br>
Subject: [PATCH net-next] net:sched: add action inheritdsfield to skbmod

net/sched: add action inheritdsfield to skbmod

The new action inheritdsfield copies the field DS of
IPv4 and IPv6 packets into skb->prioriry. This enables
later classification of packets based on the DS field.

Original idea by Jamal Hadi Salim <jhs@...atatu.com>

Signed-off-by: Qiaobin Fu <qiaobinf@...edu>
Reviewed-by: Michel Machado <michel@...irati.com.br>
---

Note that the motivation for this patch is found in the following discussion:
https://www.spinics.net/lists/netdev/msg501061.html
---

diff --git a/include/uapi/linux/tc_act/tc_skbmod.h b/include/uapi/linux/tc_act/tc_skbmod.h
index 38c072f..0718b48 100644
--- a/include/uapi/linux/tc_act/tc_skbmod.h
+++ b/include/uapi/linux/tc_act/tc_skbmod.h
@@ -19,6 +19,7 @@
 #define SKBMOD_F_SMAC	0x2
 #define SKBMOD_F_ETYPE	0x4
 #define SKBMOD_F_SWAPMAC 0x8
+#define SKBMOD_F_INHERITDSFIELD 0x10
 
 struct tc_skbmod {
 	tc_gen;
diff --git a/net/sched/act_skbmod.c b/net/sched/act_skbmod.c
index ad050d7..21d5bec 100644
--- a/net/sched/act_skbmod.c
+++ b/net/sched/act_skbmod.c
@@ -16,6 +16,9 @@
 #include <linux/rtnetlink.h>
 #include <net/netlink.h>
 #include <net/pkt_sched.h>
+#include <net/ip.h>
+#include <net/ipv6.h>
+#include <net/dsfield.h>
 
 #include <linux/tc_act/tc_skbmod.h>
 #include <net/tc_act/tc_skbmod.h>
@@ -72,6 +75,25 @@ static int tcf_skbmod_run(struct sk_buff *skb, const struct tc_action *a,
 		ether_addr_copy(eth_hdr(skb)->h_source, (u8 *)tmpaddr);
 	}
 
+	if (flags & SKBMOD_F_INHERITDSFIELD) {
+		int wlen = skb_network_offset(skb);
+		switch (tc_skb_protocol(skb)) {
+		case htons(ETH_P_IP):
+			wlen += sizeof(struct iphdr);
+			if (!pskb_may_pull(skb, wlen))
+				return TC_ACT_SHOT;
+			skb->priority = ipv4_get_dsfield(ip_hdr(skb)) >> 2;
+			break;
+
+		case htons(ETH_P_IPV6):
+			wlen += sizeof(struct ipv6hdr);
+			if (!pskb_may_pull(skb, wlen))
+				return TC_ACT_SHOT;
+			skb->priority = ipv6_get_dsfield(ipv6_hdr(skb)) >> 2;
+			break;
+		}
+	}
+
 	return action;
 }
 
@@ -127,6 +149,9 @@ static int tcf_skbmod_init(struct net *net, struct nlattr *nla,
 	if (parm->flags & SKBMOD_F_SWAPMAC)
 		lflags = SKBMOD_F_SWAPMAC;
 
+	if (parm->flags & SKBMOD_F_INHERITDSFIELD)
+		lflags |= SKBMOD_F_INHERITDSFIELD;
+
 	exists = tcf_idr_check(tn, parm->index, a, bind);
 	if (exists && bind)
 		return 0;