net/sched: add ACT_CSUM action to update packets checksums

net/sched: add ACT_CSUM action to update packets checksums

ACT_CSUM can be called just after ACT_PEDIT in order to re-compute some
altered checksums in IPv4 and IPv6 packets. The following checksums are
supported by this patch:
 - IPv4: IPv4 header, ICMP, IGMP, TCP, UDP & UDPLite
 - IPv6: ICMPv6, TCP, UDP & UDPLite
It's possible to request in the same action to update different kind of
checksums, if the packets flow mix TCP, UDP and UDPLite, ...

An example of usage is done in the associated iproute2 patch.

Version 3 changes:
 - remove useless goto instructions
 - improve IPv6 hop options decoding

Version 2 changes:
 - coding style correction
 - remove useless arguments of some functions
 - use stack in tcf_csum_dump()
 - add tcf_csum_skb_nextlayer() to factor code
Signed-off-by: Gregoire Baron <baronchon@n7mm.org>
Acked-by: jamal <hadi@cyberus.ca>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/tc_act/Kbuild

@@ -4,3 +4,4 @@ header-y += tc_mirred.h
 header-y += tc_pedit.h
 header-y += tc_nat.h
 header-y += tc_skbedit.h
+header-y += tc_csum.h

include/linux/tc_act/tc_csum.h

+#ifndef __LINUX_TC_CSUM_H
+#define __LINUX_TC_CSUM_H
+
+#include <linux/types.h>
+#include <linux/pkt_cls.h>
+
+#define TCA_ACT_CSUM 16
+
+enum {
+	TCA_CSUM_UNSPEC,
+	TCA_CSUM_PARMS,
+	TCA_CSUM_TM,
+	__TCA_CSUM_MAX
+};
+#define TCA_CSUM_MAX (__TCA_CSUM_MAX - 1)
+
+enum {
+	TCA_CSUM_UPDATE_FLAG_IPV4HDR = 1,
+	TCA_CSUM_UPDATE_FLAG_ICMP    = 2,
+	TCA_CSUM_UPDATE_FLAG_IGMP    = 4,
+	TCA_CSUM_UPDATE_FLAG_TCP     = 8,
+	TCA_CSUM_UPDATE_FLAG_UDP     = 16,
+	TCA_CSUM_UPDATE_FLAG_UDPLITE = 32
+};
+
+struct tc_csum {
+	tc_gen;
+
+	__u32 update_flags;
+};
+
+#endif /* __LINUX_TC_CSUM_H */

include/net/tc_act/tc_csum.h

+#ifndef __NET_TC_CSUM_H
+#define __NET_TC_CSUM_H
+
+#include <linux/types.h>
+#include <net/act_api.h>
+
+struct tcf_csum {
+	struct tcf_common common;
+
+	u32 update_flags;
+};
+#define to_tcf_csum(pc) \
+	container_of(pc,struct tcf_csum,common)
+
+#endif /* __NET_TC_CSUM_H */

net/sched/Kconfig

@@ -518,6 +518,16 @@ config NET_ACT_SKBEDIT
 	  To compile this code as a module, choose M here: the
 	  module will be called act_skbedit.
 
+config NET_ACT_CSUM
+        tristate "Checksum Updating"
+        depends on NET_CLS_ACT
+        ---help---
+	  Say Y here to update some common checksum after some direct
+	  packet alterations.
+
+	  To compile this code as a module, choose M here: the
+	  module will be called act_csum.
+
 config NET_CLS_IND
 	bool "Incoming device classification"
 	depends on NET_CLS_U32 || NET_CLS_FW

net/sched/Makefile

@@ -15,6 +15,7 @@ obj-$(CONFIG_NET_ACT_NAT)	+= act_nat.o
 obj-$(CONFIG_NET_ACT_PEDIT)	+= act_pedit.o
 obj-$(CONFIG_NET_ACT_SIMP)	+= act_simple.o
 obj-$(CONFIG_NET_ACT_SKBEDIT)	+= act_skbedit.o
+obj-$(CONFIG_NET_ACT_CSUM)	+= act_csum.o
 obj-$(CONFIG_NET_SCH_FIFO)	+= sch_fifo.o
 obj-$(CONFIG_NET_SCH_CBQ)	+= sch_cbq.o
 obj-$(CONFIG_NET_SCH_HTB)	+= sch_htb.o