net: sched: add em_ipt ematch for calling xtables matches

The commit a new tc ematch for using netfilter xtable matches.

This allows early classification as well as mirroning/redirecting traffic
based on logic implemented in netfilter extensions.

Current supported use case is classification based on the incoming IPSec
state used during decpsulation using the 'policy' iptables extension
(xt_policy).

The module dynamically fetches the netfilter match module and calls
it using a fake xt_action_param structure based on validated userspace
provided parameters.

As the xt_policy match does not access skb->data, no skb modifications
are needed on match.

Signed-off-by: Eyal Birger <eyal.birger@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/uapi/linux/pkt_cls.h b/include/uapi/linux/pkt_cls.h
index 46c5066..7cafb26 100644 (file)
--- a/include/uapi/linux/pkt_cls.h
+++ b/include/uapi/linux/pkt_cls.h
@@ -555,7 +555,8 @@ enum {
 #define        TCF_EM_VLAN             6
 #define        TCF_EM_CANID            7
 #define        TCF_EM_IPSET            8
-#define        TCF_EM_MAX              8
+#define        TCF_EM_IPT              9
+#define        TCF_EM_MAX              9
 
 enum {
        TCF_EM_PROG_TC

diff --git a/include/uapi/linux/tc_ematch/tc_em_ipt.h b/include/uapi/linux/tc_ematch/tc_em_ipt.h
new file mode 100644 (file)
index 0000000..49a6553
--- /dev/null
+++ b/include/uapi/linux/tc_ematch/tc_em_ipt.h
@@ -0,0 +1,20 @@
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+#ifndef __LINUX_TC_EM_IPT_H
+#define __LINUX_TC_EM_IPT_H
+
+#include <linux/types.h>
+#include <linux/pkt_cls.h>
+
+enum {
+       TCA_EM_IPT_UNSPEC,
+       TCA_EM_IPT_HOOK,
+       TCA_EM_IPT_MATCH_NAME,
+       TCA_EM_IPT_MATCH_REVISION,
+       TCA_EM_IPT_NFPROTO,
+       TCA_EM_IPT_MATCH_DATA,
+       __TCA_EM_IPT_MAX
+};
+
+#define TCA_EM_IPT_MAX (__TCA_EM_IPT_MAX - 1)
+
+#endif

diff --git a/net/sched/Kconfig b/net/sched/Kconfig
index f24a6ae..a01169f 100644 (file)
--- a/net/sched/Kconfig
+++ b/net/sched/Kconfig
@@ -658,6 +658,18 @@ config NET_EMATCH_IPSET
          To compile this code as a module, choose M here: the
          module will be called em_ipset.
 
+config NET_EMATCH_IPT
+       tristate "IPtables Matches"
+       depends on NET_EMATCH && NETFILTER && NETFILTER_XTABLES
+       ---help---
+         Say Y here to be able to classify packets based on iptables
+         matches.
+         Current supported match is "policy" which allows packet classification
+         based on IPsec policy that was used during decapsulation
+
+         To compile this code as a module, choose M here: the
+         module will be called em_ipt.
+
 config NET_CLS_ACT
        bool "Actions"
        select NET_CLS

diff --git a/net/sched/Makefile b/net/sched/Makefile
index 5b63544..8811d38 100644 (file)
--- a/net/sched/Makefile
+++ b/net/sched/Makefile
@@ -75,3 +75,4 @@ obj-$(CONFIG_NET_EMATCH_META) += em_meta.o
 obj-$(CONFIG_NET_EMATCH_TEXT)  += em_text.o
 obj-$(CONFIG_NET_EMATCH_CANID) += em_canid.o
 obj-$(CONFIG_NET_EMATCH_IPSET) += em_ipset.o
+obj-$(CONFIG_NET_EMATCH_IPT)   += em_ipt.o

diff --git a/net/sched/em_ipt.c b/net/sched/em_ipt.c
new file mode 100644 (file)
index 0000000..a5f34e9
--- /dev/null
+++ b/net/sched/em_ipt.c
@@ -0,0 +1,257 @@
+/*
+ * net/sched/em_ipt.c IPtables matches Ematch
+ *
+ * (c) 2018 Eyal Birger <eyal.birger@gmail.com>
+ *
+ * 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.
+ */
+
+#include <linux/gfp.h>
+#include <linux/module.h>
+#include <linux/types.h>
+#include <linux/kernel.h>
+#include <linux/string.h>
+#include <linux/skbuff.h>
+#include <linux/tc_ematch/tc_em_ipt.h>
+#include <linux/netfilter.h>
+#include <linux/netfilter/x_tables.h>
+#include <linux/netfilter_ipv4/ip_tables.h>
+#include <linux/netfilter_ipv6/ip6_tables.h>
+#include <net/pkt_cls.h>
+
+struct em_ipt_match {
+       const struct xt_match *match;
+       u32 hook;
+       u8 match_data[0] __aligned(8);
+};
+
+struct em_ipt_xt_match {
+       char *match_name;
+       int (*validate_match_data)(struct nlattr **tb, u8 mrev);
+};
+
+static const struct nla_policy em_ipt_policy[TCA_EM_IPT_MAX + 1] = {
+       [TCA_EM_IPT_MATCH_NAME]         = { .type = NLA_STRING,
+                                           .len = XT_EXTENSION_MAXNAMELEN },
+       [TCA_EM_IPT_MATCH_REVISION]     = { .type = NLA_U8 },
+       [TCA_EM_IPT_HOOK]               = { .type = NLA_U32 },
+       [TCA_EM_IPT_NFPROTO]            = { .type = NLA_U8 },
+       [TCA_EM_IPT_MATCH_DATA]         = { .type = NLA_UNSPEC },
+};
+
+static int check_match(struct net *net, struct em_ipt_match *im, int mdata_len)
+{
+       struct xt_mtchk_param mtpar = {};
+       union {
+               struct ipt_entry e4;
+               struct ip6t_entry e6;
+       } e = {};
+
+       mtpar.net       = net;
+       mtpar.table     = "filter";
+       mtpar.hook_mask = 1 << im->hook;
+       mtpar.family    = im->match->family;
+       mtpar.match     = im->match;
+       mtpar.entryinfo = &e;
+       mtpar.matchinfo = (void *)im->match_data;
+       return xt_check_match(&mtpar, mdata_len, 0, 0);
+}
+
+static int policy_validate_match_data(struct nlattr **tb, u8 mrev)
+{
+       if (mrev != 0) {
+               pr_err("only policy match revision 0 supported");
+               return -EINVAL;
+       }
+
+       if (nla_get_u32(tb[TCA_EM_IPT_HOOK]) != NF_INET_PRE_ROUTING) {
+               pr_err("policy can only be matched on NF_INET_PRE_ROUTING");
+               return -EINVAL;
+       }
+
+       return 0;
+}
+
+static const struct em_ipt_xt_match em_ipt_xt_matches[] = {
+       {
+               .match_name = "policy",
+               .validate_match_data = policy_validate_match_data
+       },
+       {}
+};
+
+static struct xt_match *get_xt_match(struct nlattr **tb)
+{
+       const struct em_ipt_xt_match *m;
+       struct nlattr *mname_attr;
+       u8 nfproto, mrev = 0;
+       int ret;
+
+       mname_attr = tb[TCA_EM_IPT_MATCH_NAME];
+       for (m = em_ipt_xt_matches; m->match_name; m++) {
+               if (!nla_strcmp(mname_attr, m->match_name))
+                       break;
+       }
+
+       if (!m->match_name) {
+               pr_err("Unsupported xt match");
+               return ERR_PTR(-EINVAL);
+       }
+
+       if (tb[TCA_EM_IPT_MATCH_REVISION])
+               mrev = nla_get_u8(tb[TCA_EM_IPT_MATCH_REVISION]);
+
+       ret = m->validate_match_data(tb, mrev);
+       if (ret < 0)
+               return ERR_PTR(ret);
+
+       nfproto = nla_get_u8(tb[TCA_EM_IPT_NFPROTO]);
+       return xt_request_find_match(nfproto, m->match_name, mrev);
+}
+
+static int em_ipt_change(struct net *net, void *data, int data_len,
+                        struct tcf_ematch *em)
+{
+       struct nlattr *tb[TCA_EM_IPT_MAX + 1];
+       struct em_ipt_match *im = NULL;
+       struct xt_match *match;
+       int mdata_len, ret;
+
+       ret = nla_parse(tb, TCA_EM_IPT_MAX, data, data_len, em_ipt_policy,
+                       NULL);
+       if (ret < 0)
+               return ret;
+
+       if (!tb[TCA_EM_IPT_HOOK] || !tb[TCA_EM_IPT_MATCH_NAME] ||
+           !tb[TCA_EM_IPT_MATCH_DATA] || !tb[TCA_EM_IPT_NFPROTO])
+               return -EINVAL;
+
+       match = get_xt_match(tb);
+       if (IS_ERR(match)) {
+               pr_err("unable to load match\n");
+               return PTR_ERR(match);
+       }
+
+       mdata_len = XT_ALIGN(nla_len(tb[TCA_EM_IPT_MATCH_DATA]));
+       im = kzalloc(sizeof(*im) + mdata_len, GFP_KERNEL);
+       if (!im) {
+               ret = -ENOMEM;
+               goto err;
+       }
+
+       im->match = match;
+       im->hook = nla_get_u32(tb[TCA_EM_IPT_HOOK]);
+       nla_memcpy(im->match_data, tb[TCA_EM_IPT_MATCH_DATA], mdata_len);
+
+       ret = check_match(net, im, mdata_len);
+       if (ret)
+               goto err;
+
+       em->datalen = sizeof(*im) + mdata_len;
+       em->data = (unsigned long)im;
+       return 0;
+
+err:
+       kfree(im);
+       module_put(match->me);
+       return ret;
+}
+
+static void em_ipt_destroy(struct tcf_ematch *em)
+{
+       struct em_ipt_match *im = (void *)em->data;
+
+       if (!im)
+               return;
+
+       if (im->match->destroy) {
+               struct xt_mtdtor_param par = {
+                       .net = em->net,
+                       .match = im->match,
+                       .matchinfo = im->match_data,
+                       .family = im->match->family
+               };
+               im->match->destroy(&par);
+       }
+       module_put(im->match->me);
+       kfree((void *)im);
+}
+
+static int em_ipt_match(struct sk_buff *skb, struct tcf_ematch *em,
+                       struct tcf_pkt_info *info)
+{
+       const struct em_ipt_match *im = (const void *)em->data;
+       struct xt_action_param acpar = {};
+       struct net_device *indev = NULL;
+       struct nf_hook_state state;
+       int ret;
+
+       rcu_read_lock();
+
+       if (skb->skb_iif)
+               indev = dev_get_by_index_rcu(em->net, skb->skb_iif);
+
+       nf_hook_state_init(&state, im->hook, im->match->family,
+                          indev ?: skb->dev, skb->dev, NULL, em->net, NULL);
+
+       acpar.match = im->match;
+       acpar.matchinfo = im->match_data;
+       acpar.state = &state;
+
+       ret = im->match->match(skb, &acpar);
+
+       rcu_read_unlock();
+       return ret;
+}
+
+static int em_ipt_dump(struct sk_buff *skb, struct tcf_ematch *em)
+{
+       struct em_ipt_match *im = (void *)em->data;
+
+       if (nla_put_string(skb, TCA_EM_IPT_MATCH_NAME, im->match->name) < 0)
+               return -EMSGSIZE;
+       if (nla_put_u32(skb, TCA_EM_IPT_HOOK, im->hook) < 0)
+               return -EMSGSIZE;
+       if (nla_put_u8(skb, TCA_EM_IPT_MATCH_REVISION, im->match->revision) < 0)
+               return -EMSGSIZE;
+       if (nla_put_u8(skb, TCA_EM_IPT_NFPROTO, im->match->family) < 0)
+               return -EMSGSIZE;
+       if (nla_put(skb, TCA_EM_IPT_MATCH_DATA,
+                   im->match->usersize ?: im->match->matchsize,
+                   im->match_data) < 0)
+               return -EMSGSIZE;
+
+       return 0;
+}
+
+static struct tcf_ematch_ops em_ipt_ops = {
+       .kind     = TCF_EM_IPT,
+       .change   = em_ipt_change,
+       .destroy  = em_ipt_destroy,
+       .match    = em_ipt_match,
+       .dump     = em_ipt_dump,
+       .owner    = THIS_MODULE,
+       .link     = LIST_HEAD_INIT(em_ipt_ops.link)
+};
+
+static int __init init_em_ipt(void)
+{
+       return tcf_em_register(&em_ipt_ops);
+}
+
+static void __exit exit_em_ipt(void)
+{
+       tcf_em_unregister(&em_ipt_ops);
+}
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Eyal Birger <eyal.birger@gmail.com>");
+MODULE_DESCRIPTION("TC extended match for IPtables matches");
+
+module_init(init_em_ipt);
+module_exit(exit_em_ipt);
+
+MODULE_ALIAS_TCF_EMATCH(TCF_EM_IPT);