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netfilter: nft_exthdr: Support SCTP chunks

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[ Upstream commit 133dc203d77dff617d9c4673973ef3859be2c476 ]

Chunks are SCTP header extensions similar in implementation to IPv6
extension headers or TCP options. Reusing exthdr expression to find and
extract field values from them is therefore pretty straightforward.

For now, this supports extracting data from chunks at a fixed offset
(and length) only - chunks themselves are an extensible data structure;
in order to make all fields available, a nested extension search is
needed.

Signed-off-by: Phil Sutter <phil@nwl.cc>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Stable-dep-of: 28427f368f0e ("netfilter: nft_exthdr: Fix non-linear header modification")
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Phil Sutter 2021-05-04 17:54:06 +02:00 committed by Greg Kroah-Hartman
parent 858ca19216
commit af844ba799
2 changed files with 53 additions and 0 deletions
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2
include/uapi/linux/netfilter/nf_tables.h
View File

@ -797,11 +797,13 @@ 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
* @NFT_EXTHDR_OP_SCTP: match against sctp chunks
*/
enum nft_exthdr_op {
NFT_EXTHDR_OP_IPV6,
NFT_EXTHDR_OP_TCPOPT,
NFT_EXTHDR_OP_IPV4,
NFT_EXTHDR_OP_SCTP,
__NFT_EXTHDR_OP_MAX
};
#define NFT_EXTHDR_OP_MAX (__NFT_EXTHDR_OP_MAX - 1)

51
net/netfilter/nft_exthdr.c
View File

@ -10,8 +10,10 @@
#include <linux/netlink.h>
#include <linux/netfilter.h>
#include <linux/netfilter/nf_tables.h>
#include <linux/sctp.h>
#include <net/netfilter/nf_tables_core.h>
#include <net/netfilter/nf_tables.h>
#include <net/sctp/sctp.h>
#include <net/tcp.h>
struct nft_exthdr {
@ -303,6 +305,43 @@ static void nft_exthdr_tcp_set_eval(const struct nft_expr *expr,
}
}
static void nft_exthdr_sctp_eval(const struct nft_expr *expr,
struct nft_regs *regs,
const struct nft_pktinfo *pkt)
{
unsigned int offset = pkt->xt.thoff + sizeof(struct sctphdr);
struct nft_exthdr *priv = nft_expr_priv(expr);
u32 *dest = &regs->data[priv->dreg];
const struct sctp_chunkhdr *sch;
struct sctp_chunkhdr _sch;
do {
sch = skb_header_pointer(pkt->skb, offset, sizeof(_sch), &_sch);
if (!sch || !sch->length)
break;
if (sch->type == priv->type) {
if (priv->flags & NFT_EXTHDR_F_PRESENT) {
nft_reg_store8(dest, true);
return;
}
if (priv->offset + priv->len > ntohs(sch->length) ||
offset + ntohs(sch->length) > pkt->skb->len)
break;
dest[priv->len / NFT_REG32_SIZE] = 0;
memcpy(dest, (char *)sch + priv->offset, priv->len);
return;
}
offset += SCTP_PAD4(ntohs(sch->length));
} while (offset < pkt->skb->len);
if (priv->flags & NFT_EXTHDR_F_PRESENT)
nft_reg_store8(dest, false);
else
regs->verdict.code = NFT_BREAK;
}
static const struct nla_policy nft_exthdr_policy[NFTA_EXTHDR_MAX + 1] = {
[NFTA_EXTHDR_DREG] = { .type = NLA_U32 },
[NFTA_EXTHDR_TYPE] = { .type = NLA_U8 },
@ -502,6 +541,14 @@ static const struct nft_expr_ops nft_exthdr_tcp_set_ops = {
.dump = nft_exthdr_dump_set,
};
static const struct nft_expr_ops nft_exthdr_sctp_ops = {
.type = &nft_exthdr_type,
.size = NFT_EXPR_SIZE(sizeof(struct nft_exthdr)),
.eval = nft_exthdr_sctp_eval,
.init = nft_exthdr_init,
.dump = nft_exthdr_dump,
};
static const struct nft_expr_ops *
nft_exthdr_select_ops(const struct nft_ctx *ctx,
const struct nlattr * const tb[])
@ -532,6 +579,10 @@ nft_exthdr_select_ops(const struct nft_ctx *ctx,
return &nft_exthdr_ipv4_ops;
}
break;
case NFT_EXTHDR_OP_SCTP:
if (tb[NFTA_EXTHDR_DREG])
return &nft_exthdr_sctp_ops;
break;
}
return ERR_PTR(-EOPNOTSUPP);