netdev - [PATCH net-next v3 3/4] net: sched: em_ipt: keep the user-specified nfproto and dump it

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Message-Id: <20190627081047.24537-4-nikolay@cumulusnetworks.com>
Date:   Thu, 27 Jun 2019 11:10:46 +0300
From:   Nikolay Aleksandrov <nikolay@...ulusnetworks.com>
To:     netdev@...r.kernel.org
Cc:     roopa@...ulusnetworks.com, davem@...emloft.net,
        pablo@...filter.org, xiyou.wangcong@...il.com, jiri@...nulli.us,
        jhs@...atatu.com, eyal.birger@...il.com,
        Nikolay Aleksandrov <nikolay@...ulusnetworks.com>
Subject: [PATCH net-next v3 3/4] net: sched: em_ipt: keep the user-specified nfproto and dump it

If we dump NFPROTO_UNSPEC as nfproto user-space libxtables can't handle
it and would exit with an error like:
"libxtables: unhandled NFPROTO in xtables_set_nfproto"
In order to avoid the error return the user-specified nfproto. If we
don't record it then the match family is used which can be
NFPROTO_UNSPEC. Even if we add support to mask NFPROTO_UNSPEC in
iproute2 we have to be compatible with older versions which would be
also be allowed to add NFPROTO_UNSPEC matches (e.g. addrtype after the
last patch).

v3: don't use the user nfproto for matching, only for dumping the rule,
    also don't allow the nfproto to be unspecified (explained above)
v2: adjust changes to missing patch, was patch 04 in v1

Signed-off-by: Nikolay Aleksandrov <nikolay@...ulusnetworks.com>
---
Unfortunately we still have to save the user-nfproto for dumping
otherwise we'll break user-space because it can add a rule which it
won't be able to dump later and in fact will terminate the whole dump.
I also thought about masking it but that seems more hacky, I'd prefer
to return an expected value which was passed when the rule was created.

 net/sched/em_ipt.c | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/net/sched/em_ipt.c b/net/sched/em_ipt.c
index fd7f5b288c31..3c356d6f719a 100644
--- a/net/sched/em_ipt.c
+++ b/net/sched/em_ipt.c
@@ -21,6 +21,7 @@
 struct em_ipt_match {
 	const struct xt_match *match;
 	u32 hook;
+	u8 nfproto;
 	u8 match_data[0] __aligned(8);
 };
 
@@ -115,6 +116,7 @@ static int em_ipt_change(struct net *net, void *data, int data_len,
 	struct em_ipt_match *im = NULL;
 	struct xt_match *match;
 	int mdata_len, ret;
+	u8 nfproto;
 
 	ret = nla_parse_deprecated(tb, TCA_EM_IPT_MAX, data, data_len,
 				   em_ipt_policy, NULL);
@@ -125,6 +127,15 @@ static int em_ipt_change(struct net *net, void *data, int data_len,
 	    !tb[TCA_EM_IPT_MATCH_DATA] || !tb[TCA_EM_IPT_NFPROTO])
 		return -EINVAL;
 
+	nfproto = nla_get_u8(tb[TCA_EM_IPT_NFPROTO]);
+	switch (nfproto) {
+	case NFPROTO_IPV4:
+	case NFPROTO_IPV6:
+		break;
+	default:
+		return -EINVAL;
+	}
+
 	match = get_xt_match(tb);
 	if (IS_ERR(match)) {
 		pr_err("unable to load match\n");
@@ -140,6 +151,7 @@ static int em_ipt_change(struct net *net, void *data, int data_len,
 
 	im->match = match;
 	im->hook = nla_get_u32(tb[TCA_EM_IPT_HOOK]);
+	im->nfproto = nfproto;
 	nla_memcpy(im->match_data, tb[TCA_EM_IPT_MATCH_DATA], mdata_len);
 
 	ret = check_match(net, im, mdata_len);
@@ -231,7 +243,7 @@ static int em_ipt_dump(struct sk_buff *skb, struct tcf_ematch *em)
 		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)
+	if (nla_put_u8(skb, TCA_EM_IPT_NFPROTO, im->nfproto) < 0)
 		return -EMSGSIZE;
 	if (nla_put(skb, TCA_EM_IPT_MATCH_DATA,
 		    im->match->usersize ?: im->match->matchsize,
-- 
2.21.0