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Message-Id: <20190620161959.7252-1-ssuryaextr@gmail.com>
Date: Thu, 20 Jun 2019 12:19:59 -0400
From: Stephen Suryaputra <ssuryaextr@...il.com>
To: netfilter-devel@...r.kernel.org
Cc: netdev@...r.kernel.org, Stephen Suryaputra <ssuryaextr@...il.com>
Subject: [PATCH nf-next v5] netfilter: add support for matching IPv4 options
This is the kernel change for the overall changes with this description:
Add capability to have rules matching IPv4 options. This is developed
mainly to support dropping of IP packets with loose and/or strict source
route route options.
v2: Fix style issues. Make this work with NFPROTO_INET (inet tables),
NFPROTO_BRIDGE and the NFPROTO_NETDEV families. Check skb->protocol.
Remove ability to input IP header offset for ipv4_find_option()
function (all per Pablo Neira Ayuso).
v3: Remove unused ipv4_find_option() arguments (per Pablo Neira Ayuso).
v4: Change the code to not follow ipv6_find_hdr() and just do what are
needed to support source-route, record route and router alert (per
Pablo Neira Ayuso). Fix bugs that are introduced while addressing
review comments.
v5: Add nft_exthdr_ipv4_init(). Remove redundant check of IP version
(feedback from Pablo Neira Ayuso).
Signed-off-by: Stephen Suryaputra <ssuryaextr@...il.com>
---
include/uapi/linux/netfilter/nf_tables.h | 2 +
net/ipv4/ip_options.c | 1 +
net/netfilter/nft_exthdr.c | 133 +++++++++++++++++++++++
3 files changed, 136 insertions(+)
diff --git a/include/uapi/linux/netfilter/nf_tables.h b/include/uapi/linux/netfilter/nf_tables.h
index 505393c6e959..168d741f42c5 100644
--- a/include/uapi/linux/netfilter/nf_tables.h
+++ b/include/uapi/linux/netfilter/nf_tables.h
@@ -730,10 +730,12 @@ enum nft_exthdr_flags {
*
* @NFT_EXTHDR_OP_IPV6: match against ipv6 extension headers
* @NFT_EXTHDR_OP_TCP: match against tcp options
+ * @NFT_EXTHDR_OP_IPV4: match against ipv4 options
*/
enum nft_exthdr_op {
NFT_EXTHDR_OP_IPV6,
NFT_EXTHDR_OP_TCPOPT,
+ NFT_EXTHDR_OP_IPV4,
__NFT_EXTHDR_OP_MAX
};
#define NFT_EXTHDR_OP_MAX (__NFT_EXTHDR_OP_MAX - 1)
diff --git a/net/ipv4/ip_options.c b/net/ipv4/ip_options.c
index 3db31bb9df50..ddaa01ec2bce 100644
--- a/net/ipv4/ip_options.c
+++ b/net/ipv4/ip_options.c
@@ -473,6 +473,7 @@ int __ip_options_compile(struct net *net,
*info = htonl((pp_ptr-iph)<<24);
return -EINVAL;
}
+EXPORT_SYMBOL(__ip_options_compile);
int ip_options_compile(struct net *net,
struct ip_options *opt, struct sk_buff *skb)
diff --git a/net/netfilter/nft_exthdr.c b/net/netfilter/nft_exthdr.c
index 45c8a6c07783..8032b2937c7f 100644
--- a/net/netfilter/nft_exthdr.c
+++ b/net/netfilter/nft_exthdr.c
@@ -62,6 +62,103 @@ static void nft_exthdr_ipv6_eval(const struct nft_expr *expr,
regs->verdict.code = NFT_BREAK;
}
+/* find the offset to specified option.
+ *
+ * If target header is found, its offset is set in *offset and return option
+ * number. Otherwise, return negative error.
+ *
+ * If the first fragment doesn't contain the End of Options it is considered
+ * invalid.
+ */
+static int ipv4_find_option(struct net *net, struct sk_buff *skb,
+ unsigned int *offset, int target)
+{
+ unsigned char optbuf[sizeof(struct ip_options) + 40];
+ struct ip_options *opt = (struct ip_options *)optbuf;
+ struct iphdr *iph, _iph;
+ unsigned int start;
+ bool found = false;
+ __be32 info;
+ int optlen;
+
+ iph = skb_header_pointer(skb, 0, sizeof(_iph), &_iph);
+ if (!iph)
+ return -EBADMSG;
+ start = sizeof(struct iphdr);
+
+ optlen = iph->ihl * 4 - (int)sizeof(struct iphdr);
+ if (optlen <= 0)
+ return -ENOENT;
+
+ memset(opt, 0, sizeof(struct ip_options));
+ /* Copy the options since __ip_options_compile() modifies
+ * the options.
+ */
+ if (skb_copy_bits(skb, start, opt->__data, optlen))
+ return -EBADMSG;
+ opt->optlen = optlen;
+
+ if (__ip_options_compile(net, opt, NULL, &info))
+ return -EBADMSG;
+
+ switch (target) {
+ case IPOPT_SSRR:
+ case IPOPT_LSRR:
+ if (!opt->srr)
+ break;
+ found = target == IPOPT_SSRR ? opt->is_strictroute :
+ !opt->is_strictroute;
+ if (found)
+ *offset = opt->srr + start;
+ break;
+ case IPOPT_RR:
+ if (!opt->rr)
+ break;
+ *offset = opt->rr + start;
+ found = true;
+ break;
+ case IPOPT_RA:
+ if (!opt->router_alert)
+ break;
+ *offset = opt->router_alert + start;
+ found = true;
+ break;
+ default:
+ return -EOPNOTSUPP;
+ }
+ return found ? target : -ENOENT;
+}
+
+static void nft_exthdr_ipv4_eval(const struct nft_expr *expr,
+ struct nft_regs *regs,
+ const struct nft_pktinfo *pkt)
+{
+ struct nft_exthdr *priv = nft_expr_priv(expr);
+ u32 *dest = ®s->data[priv->dreg];
+ struct sk_buff *skb = pkt->skb;
+ unsigned int offset;
+ int err;
+
+ if (skb->protocol != htons(ETH_P_IP))
+ goto err;
+
+ err = ipv4_find_option(nft_net(pkt), skb, &offset, priv->type);
+ if (priv->flags & NFT_EXTHDR_F_PRESENT) {
+ *dest = (err >= 0);
+ return;
+ } else if (err < 0) {
+ goto err;
+ }
+ offset += priv->offset;
+
+ dest[priv->len / NFT_REG32_SIZE] = 0;
+ if (skb_copy_bits(pkt->skb, offset, dest, priv->len) < 0)
+ goto err;
+ return;
+err:
+ regs->verdict.code = NFT_BREAK;
+}
+
static void *
nft_tcp_header_pointer(const struct nft_pktinfo *pkt,
unsigned int len, void *buffer, unsigned int *tcphdr_len)
@@ -315,6 +412,28 @@ static int nft_exthdr_tcp_set_init(const struct nft_ctx *ctx,
return nft_validate_register_load(priv->sreg, priv->len);
}
+static int nft_exthdr_ipv4_init(const struct nft_ctx *ctx,
+ const struct nft_expr *expr,
+ const struct nlattr * const tb[])
+{
+ struct nft_exthdr *priv = nft_expr_priv(expr);
+ int err = nft_exthdr_init(ctx, expr, tb);
+
+ if (err < 0)
+ return err;
+
+ switch (priv->type) {
+ case IPOPT_SSRR:
+ case IPOPT_LSRR:
+ case IPOPT_RR:
+ case IPOPT_RA:
+ break;
+ default:
+ return -EOPNOTSUPP;
+ }
+ return 0;
+}
+
static int nft_exthdr_dump_common(struct sk_buff *skb, const struct nft_exthdr *priv)
{
if (nla_put_u8(skb, NFTA_EXTHDR_TYPE, priv->type))
@@ -361,6 +480,14 @@ static const struct nft_expr_ops nft_exthdr_ipv6_ops = {
.dump = nft_exthdr_dump,
};
+static const struct nft_expr_ops nft_exthdr_ipv4_ops = {
+ .type = &nft_exthdr_type,
+ .size = NFT_EXPR_SIZE(sizeof(struct nft_exthdr)),
+ .eval = nft_exthdr_ipv4_eval,
+ .init = nft_exthdr_ipv4_init,
+ .dump = nft_exthdr_dump,
+};
+
static const struct nft_expr_ops nft_exthdr_tcp_ops = {
.type = &nft_exthdr_type,
.size = NFT_EXPR_SIZE(sizeof(struct nft_exthdr)),
@@ -401,6 +528,12 @@ nft_exthdr_select_ops(const struct nft_ctx *ctx,
if (tb[NFTA_EXTHDR_DREG])
return &nft_exthdr_ipv6_ops;
break;
+ case NFT_EXTHDR_OP_IPV4:
+ if (ctx->family != NFPROTO_IPV6) {
+ if (tb[NFTA_EXTHDR_DREG])
+ return &nft_exthdr_ipv4_ops;
+ }
+ break;
}
return ERR_PTR(-EOPNOTSUPP);
--
2.17.1
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