This allows setting 2 and 4 byte quantities in the tcp option space.
This allows native replacement for xt_TCPMSS in nf_tables.
Todo:
-TCPOPTSTRIP equivalent
-possibly restrict write support so we can't generate
invalid options (e.g., don't allow write to kind,len).
Signed-off-by: Florian Westphal <f...@strlen.de>
---
include/uapi/linux/netfilter/nf_tables.h | 4 +-
net/netfilter/nft_exthdr.c | 161 ++++++++++++++++++++++++++++++-
2 files changed, 162 insertions(+), 3 deletions(-)
diff --git a/include/uapi/linux/netfilter/nf_tables.h
b/include/uapi/linux/netfilter/nf_tables.h
index 683f6f88fcac..4766f5091b5f 100644
--- a/include/uapi/linux/netfilter/nf_tables.h
+++ b/include/uapi/linux/netfilter/nf_tables.h
@@ -731,7 +731,8 @@ enum nft_exthdr_op {
* @NFTA_EXTHDR_OFFSET: extension header offset (NLA_U32)
* @NFTA_EXTHDR_LEN: extension header length (NLA_U32)
* @NFTA_EXTHDR_FLAGS: extension header flags (NLA_U32)
- * @NFTA_EXTHDR_OP: option match type (NLA_U8)
+ * @NFTA_EXTHDR_OP: option match type (NLA_U32)
+ * @NFTA_EXTHDR_SREG: option match type (NLA_U32)
*/
enum nft_exthdr_attributes {
NFTA_EXTHDR_UNSPEC,
@@ -741,6 +742,7 @@ enum nft_exthdr_attributes {
NFTA_EXTHDR_LEN,
NFTA_EXTHDR_FLAGS,
NFTA_EXTHDR_OP,
+ NFTA_EXTHDR_SREG,
__NFTA_EXTHDR_MAX
};
#define NFTA_EXTHDR_MAX (__NFTA_EXTHDR_MAX - 1)
diff --git a/net/netfilter/nft_exthdr.c b/net/netfilter/nft_exthdr.c
index e3a6eebe7e0c..214211699f8d 100644
--- a/net/netfilter/nft_exthdr.c
+++ b/net/netfilter/nft_exthdr.c
@@ -8,6 +8,7 @@
* Development of this code funded by Astaro AG (http://www.astaro.com/)
*/
+#include <asm/unaligned.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/module.h>
@@ -23,6 +24,7 @@ struct nft_exthdr {
u8 len;
u8 op;
enum nft_registers dreg:8;
+ enum nft_registers sreg:8;
u8 flags;
};
@@ -124,6 +126,88 @@ static void nft_exthdr_tcp_eval(const struct nft_expr
*expr,
regs->verdict.code = NFT_BREAK;
}
+static void nft_exthdr_tcp_set_eval(const struct nft_expr *expr,
+ struct nft_regs *regs,
+ const struct nft_pktinfo *pkt)
+{
+ u8 buff[sizeof(struct tcphdr) + MAX_TCP_OPTION_SPACE];
+ struct nft_exthdr *priv = nft_expr_priv(expr);
+ unsigned int i, optl, tcphdr_len, offset;
+ struct tcphdr *tcph;
+ u8 *opt;
+ u32 src;
+
+ tcph = nft_tcp_header_pointer(pkt, sizeof(buff), buff, &tcphdr_len);
+ if (!tcph)
+ return;
+
+ opt = (u8 *)tcph;
+ for (i = sizeof(*tcph); i < tcphdr_len - 1; i += optl) {
+ union {
+ u8 octet;
+ __be16 v16;
+ __be32 v32;
+ } old, new;
+
+ optl = optlen(opt, i);
+
+ if (priv->type != opt[i])
+ continue;
+
+ if (i + optl > tcphdr_len || priv->len + priv->offset > optl)
+ return;
+
+ if (!skb_make_writable(pkt->skb, pkt->xt.thoff + i + priv->len))
+ return;
+
+ tcph = nft_tcp_header_pointer(pkt, sizeof(buff), buff,
+ &tcphdr_len);
+ if (!tcph)
+ return;
+
+ src = regs->data[priv->sreg];
+ offset = i + priv->offset;
+
+ switch (priv->len) {
+ case 2:
+ old.v16 = get_unaligned((u16 *)(opt + offset));
+ new.v16 = src;
+
+ if (old.v16 == new.v16)
+ return;
+
+ switch (priv->type) {
+ case TCPOPT_MSS:
+ /* increase can cause connection to stall */
+ if (ntohs(old.v16) <= ntohs(new.v16))
+ return;
+ break;
+ }
+
+ put_unaligned(new.v16, (u16*)(opt + offset));
+ inet_proto_csum_replace2(&tcph->check, pkt->skb,
+ old.v16, new.v16, false);
+ break;
+ case 4:
+ new.v32 = src;
+ old.v32 = get_unaligned((u32 *)(opt + offset));
+
+ if (old.v32 == new.v32)
+ return;
+
+ put_unaligned(new.v32, (u32*)(opt + offset));
+ inet_proto_csum_replace4(&tcph->check, pkt->skb,
+ old.v32, new.v32, false);
+ break;
+ default:
+ WARN_ON_ONCE(1);
+ break;
+ }
+
+ return;
+ }
+}
+
static const struct nla_policy nft_exthdr_policy[NFTA_EXTHDR_MAX + 1] = {
[NFTA_EXTHDR_DREG] = { .type = NLA_U32 },
[NFTA_EXTHDR_TYPE] = { .type = NLA_U8 },
@@ -180,6 +264,52 @@ static int nft_exthdr_init(const struct nft_ctx *ctx,
NFT_DATA_VALUE, priv->len);
}
+static int nft_exthdr_tcp_set_init(const struct nft_ctx *ctx,
+ const struct nft_expr *expr,
+ const struct nlattr * const tb[])
+{
+ struct nft_exthdr *priv = nft_expr_priv(expr);
+ u32 offset, len, flags = 0, op = NFT_EXTHDR_OP_IPV6;
+ int err;
+
+ if (!tb[NFTA_EXTHDR_SREG] ||
+ !tb[NFTA_EXTHDR_TYPE] ||
+ !tb[NFTA_EXTHDR_OFFSET] ||
+ !tb[NFTA_EXTHDR_LEN])
+ return -EINVAL;
+
+ if (tb[NFTA_EXTHDR_DREG] || tb[NFTA_EXTHDR_FLAGS])
+ return -EINVAL;
+
+ err = nft_parse_u32_check(tb[NFTA_EXTHDR_OFFSET], U8_MAX, &offset);
+ if (err < 0)
+ return err;
+
+ err = nft_parse_u32_check(tb[NFTA_EXTHDR_LEN], U8_MAX, &len);
+ if (err < 0)
+ return err;
+
+ switch (len) {
+ case 2: break;
+ case 4: break;
+ default:
+ return -EOPNOTSUPP;
+ }
+
+ err = nft_parse_u32_check(tb[NFTA_EXTHDR_OP], U8_MAX, &op);
+ if (err < 0)
+ return err;
+
+ priv->type = nla_get_u8(tb[NFTA_EXTHDR_TYPE]);
+ priv->offset = offset;
+ priv->len = len;
+ priv->sreg = nft_parse_register(tb[NFTA_EXTHDR_SREG]);
+ priv->flags = flags;
+ priv->op = op;
+
+ return nft_validate_register_load(priv->sreg, priv->len);
+}
+
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))
@@ -208,6 +338,16 @@ static int nft_exthdr_dump(struct sk_buff *skb, const
struct nft_expr *expr)
return nft_exthdr_dump_common(skb, priv);
}
+static int nft_exthdr_dump_set(struct sk_buff *skb, const struct nft_expr
*expr)
+{
+ const struct nft_exthdr *priv = nft_expr_priv(expr);
+
+ if (nft_dump_register(skb, NFTA_EXTHDR_SREG, priv->sreg))
+ return -1;
+
+ return nft_exthdr_dump_common(skb, priv);
+}
+
static struct nft_expr_type nft_exthdr_type;
static const struct nft_expr_ops nft_exthdr_ipv6_ops = {
.type = &nft_exthdr_type,
@@ -225,6 +365,14 @@ static const struct nft_expr_ops nft_exthdr_tcp_ops = {
.dump = nft_exthdr_dump,
};
+static const struct nft_expr_ops nft_exthdr_tcp_set_ops = {
+ .type = &nft_exthdr_type,
+ .size = NFT_EXPR_SIZE(sizeof(struct nft_exthdr)),
+ .eval = nft_exthdr_tcp_set_eval,
+ .init = nft_exthdr_tcp_set_init,
+ .dump = nft_exthdr_dump_set,
+};
+
static const struct nft_expr_ops *
nft_exthdr_select_ops(const struct nft_ctx *ctx,
const struct nlattr * const tb[])
@@ -234,12 +382,21 @@ nft_exthdr_select_ops(const struct nft_ctx *ctx,
if (!tb[NFTA_EXTHDR_OP])
return &nft_exthdr_ipv6_ops;
+ if (tb[NFTA_EXTHDR_SREG] && tb[NFTA_EXTHDR_DREG])
+ return ERR_PTR(-EOPNOTSUPP);
+
op = ntohl(nla_get_u32(tb[NFTA_EXTHDR_OP]));
switch (op) {
case NFT_EXTHDR_OP_TCPOPT:
- return &nft_exthdr_tcp_ops;
+ if (tb[NFTA_EXTHDR_SREG])
+ return &nft_exthdr_tcp_set_ops;
+ if (tb[NFTA_EXTHDR_DREG])
+ return &nft_exthdr_tcp_ops;
+ break;
case NFT_EXTHDR_OP_IPV6:
- return &nft_exthdr_ipv6_ops;
+ if (tb[NFTA_EXTHDR_DREG])
+ return &nft_exthdr_ipv6_ops;
+ break;
}
return ERR_PTR(-EOPNOTSUPP);
--
2.13.0
--
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