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netfilter: nf_tables: 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.

Signed-off-by: Stephen Suryaputra <ssuryaextr@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
alistair/sunxi64-5.4-dsi
Stephen Suryaputra 2019-06-20 12:19:59 -04:00 committed by Pablo Neira Ayuso
parent f76c7bfca4
commit dbb5281a1f
3 changed files with 136 additions and 0 deletions
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2
include/uapi/linux/netfilter/nf_tables.h
View File

@ -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)

1
net/ipv4/ip_options.c
View File

@ -473,6 +473,7 @@ error:
*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)

133
net/netfilter/nft_exthdr.c
View File

@ -62,6 +62,103 @@ err:
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 = &regs->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);