It allows matching packets based on Segment Routing Header
(SRH) information.
The implementation considers revision 7 of the SRH draft.
https://tools.ietf.org/html/draft-ietf-6man-segment-routing-header-07
Currently supported match options include:
(1) Next Header
(2) Hdr Ext Len
(3) Segments Left
(4) Last Entry
(5) Tag value of SRH
Signed-off-by: Ahmed Abdelsalam <[email protected]>
---
include/uapi/linux/netfilter_ipv6/ip6t_srh.h | 57 ++++++++++
net/ipv6/netfilter/Kconfig | 9 ++
net/ipv6/netfilter/Makefile | 1 +
net/ipv6/netfilter/ip6t_srh.c | 161 +++++++++++++++++++++++++++
4 files changed, 228 insertions(+)
create mode 100644 include/uapi/linux/netfilter_ipv6/ip6t_srh.h
create mode 100644 net/ipv6/netfilter/ip6t_srh.c
diff --git a/include/uapi/linux/netfilter_ipv6/ip6t_srh.h b/include/uapi/linux/netfilter_ipv6/ip6t_srh.h
new file mode 100644
index 0000000..cebf4e8
--- /dev/null
+++ b/include/uapi/linux/netfilter_ipv6/ip6t_srh.h
@@ -0,0 +1,57 @@
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+#ifndef _IP6T_SRH_H
+#define _IP6T_SRH_H
+
+#include <linux/types.h>
+#include <linux/netfilter.h>
+
+/* Values for "mt_flags" field in struct ip6t_srh */
+#define IP6T_SRH_NEXTHDR 0x0001
+#define IP6T_SRH_LEN_EQ 0x0002
+#define IP6T_SRH_LEN_GT 0x0004
+#define IP6T_SRH_LEN_LT 0x0008
+#define IP6T_SRH_SEGS_EQ 0x0010
+#define IP6T_SRH_SEGS_GT 0x0020
+#define IP6T_SRH_SEGS_LT 0x0040
+#define IP6T_SRH_LAST_EQ 0x0080
+#define IP6T_SRH_LAST_GT 0x0100
+#define IP6T_SRH_LAST_LT 0x0200
+#define IP6T_SRH_TAG 0x0400
+#define IP6T_SRH_MASK 0x07FF
+
+/* Values for "mt_invflags" field in struct ip6t_srh */
+#define IP6T_SRH_INV_NEXTHDR 0x0001
+#define IP6T_SRH_INV_LEN_EQ 0x0002
+#define IP6T_SRH_INV_LEN_GT 0x0004
+#define IP6T_SRH_INV_LEN_LT 0x0008
+#define IP6T_SRH_INV_SEGS_EQ 0x0010
+#define IP6T_SRH_INV_SEGS_GT 0x0020
+#define IP6T_SRH_INV_SEGS_LT 0x0040
+#define IP6T_SRH_INV_LAST_EQ 0x0080
+#define IP6T_SRH_INV_LAST_GT 0x0100
+#define IP6T_SRH_INV_LAST_LT 0x0200
+#define IP6T_SRH_INV_TAG 0x0400
+#define IP6T_SRH_INV_MASK 0x07FF
+
+/**
+ * struct ip6t_srh - SRH match options
+ * @ next_hdr: Next header field of SRH
+ * @ hdr_len: Extension header length field of SRH
+ * @ segs_left: Segments left field of SRH
+ * @ last_entry: Last entry field of SRH
+ * @ tag: Tag field of SRH
+ * @ mt_flags: match options
+ * @ mt_invflags: Invert the sense of match options
+ */
+
+struct ip6t_srh {
+ __u8 next_hdr;
+ __u8 hdr_len;
+ __u8 segs_left;
+ __u8 last_entry;
+ __u16 tag;
+ __u16 mt_flags;
+ __u16 mt_invflags;
+};
+
+#endif /*_IP6T_SRH_H*/
diff --git a/net/ipv6/netfilter/Kconfig b/net/ipv6/netfilter/Kconfig
index 6acb2ee..e1818eb 100644
--- a/net/ipv6/netfilter/Kconfig
+++ b/net/ipv6/netfilter/Kconfig
@@ -232,6 +232,15 @@ config IP6_NF_MATCH_RT
To compile it as a module, choose M here. If unsure, say N.
+config IP6_NF_MATCH_SRH
+ tristate '"srh" Segment Routing header match support'
+ depends on NETFILTER_ADVANCED
+ help
+ srh matching allows you to match packets based on the segment
+ routing header of the packet.
+
+ To compile it as a module, choose M here. If unsure, say N.
+
# The targets
config IP6_NF_TARGET_HL
tristate '"HL" hoplimit target support'
diff --git a/net/ipv6/netfilter/Makefile b/net/ipv6/netfilter/Makefile
index c6ee0cd..e0d51a9 100644
--- a/net/ipv6/netfilter/Makefile
+++ b/net/ipv6/netfilter/Makefile
@@ -54,6 +54,7 @@ obj-$(CONFIG_IP6_NF_MATCH_MH) += ip6t_mh.o
obj-$(CONFIG_IP6_NF_MATCH_OPTS) += ip6t_hbh.o
obj-$(CONFIG_IP6_NF_MATCH_RPFILTER) += ip6t_rpfilter.o
obj-$(CONFIG_IP6_NF_MATCH_RT) += ip6t_rt.o
+obj-$(CONFIG_IP6_NF_MATCH_SRH) += ip6t_srh.o
# targets
obj-$(CONFIG_IP6_NF_TARGET_MASQUERADE) += ip6t_MASQUERADE.o
diff --git a/net/ipv6/netfilter/ip6t_srh.c b/net/ipv6/netfilter/ip6t_srh.c
new file mode 100644
index 0000000..9642164
--- /dev/null
+++ b/net/ipv6/netfilter/ip6t_srh.c
@@ -0,0 +1,161 @@
+/* Kernel module to match Segment Routing Header (SRH) parameters. */
+
+/* Author:
+ * Ahmed Abdelsalam <[email protected]>
+ *
+ * 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.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+#include <linux/module.h>
+#include <linux/skbuff.h>
+#include <linux/ipv6.h>
+#include <linux/types.h>
+#include <net/ipv6.h>
+#include <net/seg6.h>
+
+#include <linux/netfilter/x_tables.h>
+#include <linux/netfilter_ipv6/ip6t_srh.h>
+#include <linux/netfilter_ipv6/ip6_tables.h>
+
+/* Test a struct->mt_invflags and a boolean for inequality */
+#define NF_SRH_INVF(ptr, flag, boolean) \
+ ((boolean) ^ !!((ptr)->mt_invflags & (flag)))
+
+static bool srh_mt6(const struct sk_buff *skb, struct xt_action_param *par)
+{
+ const struct ip6t_srh *srhinfo = par->matchinfo;
+ struct ipv6_sr_hdr *srh;
+ struct ipv6_sr_hdr _srh;
+ int hdrlen, srhoff = 0;
+
+ if (ipv6_find_hdr(skb, &srhoff, IPPROTO_ROUTING, NULL, NULL) < 0)
+ return false;
+ srh = skb_header_pointer(skb, srhoff, sizeof(_srh), &_srh);
+ if (!srh)
+ return false;
+
+ hdrlen = ipv6_optlen(srh);
+ if (skb->len - srhoff < hdrlen)
+ return false;
+
+ if (srh->type != IPV6_SRCRT_TYPE_4)
+ return false;
+
+ if (srh->segments_left > srh->first_segment)
+ return false;
+
+ /* Next Header matching */
+ if (srhinfo->mt_flags & IP6T_SRH_NEXTHDR)
+ if (NF_SRH_INVF(srhinfo, IP6T_SRH_INV_NEXTHDR,
+ !(srh->nexthdr == srhinfo->next_hdr)))
+ return false;
+
+ /* Header Extension Length matching */
+ if (srhinfo->mt_flags & IP6T_SRH_LEN_EQ)
+ if (NF_SRH_INVF(srhinfo, IP6T_SRH_INV_LEN_EQ,
+ !(srh->hdrlen == srhinfo->hdr_len)))
+ return false;
+
+ if (srhinfo->mt_flags & IP6T_SRH_LEN_GT)
+ if (NF_SRH_INVF(srhinfo, IP6T_SRH_INV_LEN_GT,
+ !(srh->hdrlen > srhinfo->hdr_len)))
+ return false;
+
+ if (srhinfo->mt_flags & IP6T_SRH_LEN_LT)
+ if (NF_SRH_INVF(srhinfo, IP6T_SRH_INV_LEN_LT,
+ !(srh->hdrlen < srhinfo->hdr_len)))
+ return false;
+
+ /* Segments Left matching */
+ if (srhinfo->mt_flags & IP6T_SRH_SEGS_EQ)
+ if (NF_SRH_INVF(srhinfo, IP6T_SRH_INV_SEGS_EQ,
+ !(srh->segments_left == srhinfo->segs_left)))
+ return false;
+
+ if (srhinfo->mt_flags & IP6T_SRH_SEGS_GT)
+ if (NF_SRH_INVF(srhinfo, IP6T_SRH_INV_SEGS_GT,
+ !(srh->segments_left > srhinfo->segs_left)))
+ return false;
+
+ if (srhinfo->mt_flags & IP6T_SRH_SEGS_LT)
+ if (NF_SRH_INVF(srhinfo, IP6T_SRH_INV_SEGS_LT,
+ !(srh->segments_left < srhinfo->segs_left)))
+ return false;
+
+ /**
+ * Last Entry matching
+ * Last_Entry field was introduced in revision 6 of the SRH draft.
+ * It was called First_Segment in the previous revision
+ */
+ if (srhinfo->mt_flags & IP6T_SRH_LAST_EQ)
+ if (NF_SRH_INVF(srhinfo, IP6T_SRH_INV_LAST_EQ,
+ !(srh->first_segment == srhinfo->last_entry)))
+ return false;
+
+ if (srhinfo->mt_flags & IP6T_SRH_LAST_GT)
+ if (NF_SRH_INVF(srhinfo, IP6T_SRH_INV_LAST_GT,
+ !(srh->first_segment > srhinfo->last_entry)))
+ return false;
+
+ if (srhinfo->mt_flags & IP6T_SRH_LAST_LT)
+ if (NF_SRH_INVF(srhinfo, IP6T_SRH_INV_LAST_LT,
+ !(srh->first_segment < srhinfo->last_entry)))
+ return false;
+
+ /**
+ * Tag matchig
+ * Tag field was introduced in revision 6 of the SRH draft.
+ */
+ if (srhinfo->mt_flags & IP6T_SRH_TAG)
+ if (NF_SRH_INVF(srhinfo, IP6T_SRH_INV_TAG,
+ !(srh->tag == srhinfo->tag)))
+ return false;
+ return true;
+}
+
+static int srh_mt6_check(const struct xt_mtchk_param *par)
+{
+ const struct ip6t_srh *srhinfo = par->matchinfo;
+
+ if (srhinfo->mt_flags & ~IP6T_SRH_MASK) {
+ pr_err("unknown srh match flags %X\n", srhinfo->mt_flags);
+ return -EINVAL;
+ }
+
+ if (srhinfo->mt_invflags & ~IP6T_SRH_INV_MASK) {
+ pr_err("unknown srh invflags %X\n", srhinfo->mt_invflags);
+ return -EINVAL;
+ }
+
+ return 0;
+}
+
+static struct xt_match srh_mt6_reg __read_mostly = {
+ .name = "srh",
+ .family = NFPROTO_IPV6,
+ .match = srh_mt6,
+ .matchsize = sizeof(struct ip6t_srh),
+ .checkentry = srh_mt6_check,
+ .me = THIS_MODULE,
+};
+
+static int __init srh_mt6_init(void)
+{
+ return xt_register_match(&srh_mt6_reg);
+}
+
+static void __exit srh_mt6_exit(void)
+{
+ xt_unregister_match(&srh_mt6_reg);
+}
+
+module_init(srh_mt6_init);
+module_exit(srh_mt6_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("Xtables: IPv6 Segment Routing Header match");
+MODULE_AUTHOR("Ahmed Abdelsalam <[email protected]>");
--
2.1.4
On Sun, Jan 07, 2018 at 07:22:02PM +0100, Ahmed Abdelsalam wrote:
> It allows matching packets based on Segment Routing Header
> (SRH) information.
> The implementation considers revision 7 of the SRH draft.
> https://tools.ietf.org/html/draft-ietf-6man-segment-routing-header-07
>
> Currently supported match options include:
> (1) Next Header
> (2) Hdr Ext Len
> (3) Segments Left
> (4) Last Entry
> (5) Tag value of SRH
net/ipv6/netfilter/ip6t_srh.c: In function ‘srh_mt6’:
net/ipv6/netfilter/ip6t_srh.c:115:10: error: ‘struct ipv6_sr_hdr’ has
no member named ‘tag’
!(srh->tag == srhinfo->tag)))
^
net/ipv6/netfilter/ip6t_srh.c:26:4: note: in definition of macro
‘NF_SRH_INVF’
((boolean) ^ !!((ptr)->mt_invflags & (flag)))
^
Something breaks compilation here.
On Mon, Jan 08, 2018 at 02:45:16PM +0100, Ahmed AbdelSalam wrote:
>
> > On 8 Jan 2018, at 14:37, Pablo Neira Ayuso <[email protected]> wrote:
> >
> > On Sun, Jan 07, 2018 at 07:22:02PM +0100, Ahmed Abdelsalam wrote:
> >> It allows matching packets based on Segment Routing Header
> >> (SRH) information.
> >> The implementation considers revision 7 of the SRH draft.
> >> https://tools.ietf.org/html/draft-ietf-6man-segment-routing-header-07
> >>
> >> Currently supported match options include:
> >> (1) Next Header
> >> (2) Hdr Ext Len
> >> (3) Segments Left
> >> (4) Last Entry
> >> (5) Tag value of SRH
> >
> > net/ipv6/netfilter/ip6t_srh.c: In function ‘srh_mt6’:
> > net/ipv6/netfilter/ip6t_srh.c:115:10: error: ‘struct ipv6_sr_hdr’ has
> > no member named ‘tag’
> > !(srh->tag == srhinfo->tag)))
> > ^
> > net/ipv6/netfilter/ip6t_srh.c:26:4: note: in definition of macro
> > ‘NF_SRH_INVF’
> > ((boolean) ^ !!((ptr)->mt_invflags & (flag)))
> > ^
> >
> > Something breaks compilation here.
>
>
> This patch is based on David Miller net-next tree.
> The reason for the compilation error is that you don’t have in your tree the following patch
> ipv6: sr: update the struct ipv6_sr_hdr (https://patchwork.ozlabs.org/patch/838198/ <https://patchwork.ozlabs.org/patch/838198/>).
> In this patch the “tag” field was introduced to replace the reserved bits of SRH
OK. I'll included this in the next batch, once nf-next gets in sync
with net-next.
Thanks for explaining.
On Sun, Jan 07, 2018 at 07:22:02PM +0100, Ahmed Abdelsalam wrote:
> It allows matching packets based on Segment Routing Header
> (SRH) information.
> The implementation considers revision 7 of the SRH draft.
> https://tools.ietf.org/html/draft-ietf-6man-segment-routing-header-07
>
> Currently supported match options include:
> (1) Next Header
> (2) Hdr Ext Len
> (3) Segments Left
> (4) Last Entry
> (5) Tag value of SRH
Now applied to nf-next, thanks for your patience.