netfilter: nf_reject_ipv6: split nf_send_reset6() in smaller functions
That can be reused by the reject bridge expression to build the reject packet. The new functions are: * nf_reject_ip6_tcphdr_get(): to sanitize and to obtain the TCP header. * nf_reject_ip6hdr_put(): to build the IPv6 header. * nf_reject_ip6_tcphdr_put(): to build the TCP header. Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
This commit is contained in:
Pablo Neira Ayuso
parent
052b9498ee
commit
8bfcdf6671
|
|
@ -15,4 +15,14 @@ nf_send_unreach6(struct net *net, struct sk_buff *skb_in, unsigned char code,
|
|||
|
||||
void nf_send_reset6(struct net *net, struct sk_buff *oldskb, int hook);
|
||||
|
||||
const struct tcphdr *nf_reject_ip6_tcphdr_get(struct sk_buff *oldskb,
|
||||
struct tcphdr *otcph,
|
||||
unsigned int *otcplen, int hook);
|
||||
struct ipv6hdr *nf_reject_ip6hdr_put(struct sk_buff *nskb,
|
||||
const struct sk_buff *oldskb,
|
||||
__be16 protocol, int hoplimit);
|
||||
void nf_reject_ip6_tcphdr_put(struct sk_buff *nskb,
|
||||
const struct sk_buff *oldskb,
|
||||
const struct tcphdr *oth, unsigned int otcplen);
|
||||
|
||||
#endif /* _IPV6_NF_REJECT_H */
|
||||
|
|
|
|||
|
|
@ -12,20 +12,131 @@
|
|||
#include <net/ip6_fib.h>
|
||||
#include <net/ip6_checksum.h>
|
||||
#include <linux/netfilter_ipv6.h>
|
||||
#include <net/netfilter/ipv6/nf_reject.h>
|
||||
|
||||
const struct tcphdr *nf_reject_ip6_tcphdr_get(struct sk_buff *oldskb,
|
||||
struct tcphdr *otcph,
|
||||
unsigned int *otcplen, int hook)
|
||||
{
|
||||
const struct ipv6hdr *oip6h = ipv6_hdr(oldskb);
|
||||
u8 proto;
|
||||
__be16 frag_off;
|
||||
int tcphoff;
|
||||
|
||||
proto = oip6h->nexthdr;
|
||||
tcphoff = ipv6_skip_exthdr(oldskb, ((u8*)(oip6h+1) - oldskb->data),
|
||||
&proto, &frag_off);
|
||||
|
||||
if ((tcphoff < 0) || (tcphoff > oldskb->len)) {
|
||||
pr_debug("Cannot get TCP header.\n");
|
||||
return NULL;
|
||||
}
|
||||
|
||||
*otcplen = oldskb->len - tcphoff;
|
||||
|
||||
/* IP header checks: fragment, too short. */
|
||||
if (proto != IPPROTO_TCP || *otcplen < sizeof(struct tcphdr)) {
|
||||
pr_debug("proto(%d) != IPPROTO_TCP or too short (len = %d)\n",
|
||||
proto, *otcplen);
|
||||
return NULL;
|
||||
}
|
||||
|
||||
otcph = skb_header_pointer(oldskb, tcphoff, sizeof(struct tcphdr),
|
||||
otcph);
|
||||
if (otcph == NULL)
|
||||
return NULL;
|
||||
|
||||
/* No RST for RST. */
|
||||
if (otcph->rst) {
|
||||
pr_debug("RST is set\n");
|
||||
return NULL;
|
||||
}
|
||||
|
||||
/* Check checksum. */
|
||||
if (nf_ip6_checksum(oldskb, hook, tcphoff, IPPROTO_TCP)) {
|
||||
pr_debug("TCP checksum is invalid\n");
|
||||
return NULL;
|
||||
}
|
||||
|
||||
return otcph;
|
||||
}
|
||||
EXPORT_SYMBOL_GPL(nf_reject_ip6_tcphdr_get);
|
||||
|
||||
struct ipv6hdr *nf_reject_ip6hdr_put(struct sk_buff *nskb,
|
||||
const struct sk_buff *oldskb,
|
||||
__be16 protocol, int hoplimit)
|
||||
{
|
||||
struct ipv6hdr *ip6h;
|
||||
const struct ipv6hdr *oip6h = ipv6_hdr(oldskb);
|
||||
#define DEFAULT_TOS_VALUE 0x0U
|
||||
const __u8 tclass = DEFAULT_TOS_VALUE;
|
||||
|
||||
skb_put(nskb, sizeof(struct ipv6hdr));
|
||||
skb_reset_network_header(nskb);
|
||||
ip6h = ipv6_hdr(nskb);
|
||||
ip6_flow_hdr(ip6h, tclass, 0);
|
||||
ip6h->hop_limit = hoplimit;
|
||||
ip6h->nexthdr = protocol;
|
||||
ip6h->saddr = oip6h->daddr;
|
||||
ip6h->daddr = oip6h->saddr;
|
||||
|
||||
nskb->protocol = htons(ETH_P_IPV6);
|
||||
|
||||
return ip6h;
|
||||
}
|
||||
EXPORT_SYMBOL_GPL(nf_reject_ip6hdr_put);
|
||||
|
||||
void nf_reject_ip6_tcphdr_put(struct sk_buff *nskb,
|
||||
const struct sk_buff *oldskb,
|
||||
const struct tcphdr *oth, unsigned int otcplen)
|
||||
{
|
||||
struct tcphdr *tcph;
|
||||
int needs_ack;
|
||||
|
||||
skb_reset_transport_header(nskb);
|
||||
tcph = (struct tcphdr *)skb_put(nskb, sizeof(struct tcphdr));
|
||||
/* Truncate to length (no data) */
|
||||
tcph->doff = sizeof(struct tcphdr)/4;
|
||||
tcph->source = oth->dest;
|
||||
tcph->dest = oth->source;
|
||||
|
||||
if (oth->ack) {
|
||||
needs_ack = 0;
|
||||
tcph->seq = oth->ack_seq;
|
||||
tcph->ack_seq = 0;
|
||||
} else {
|
||||
needs_ack = 1;
|
||||
tcph->ack_seq = htonl(ntohl(oth->seq) + oth->syn + oth->fin +
|
||||
otcplen - (oth->doff<<2));
|
||||
tcph->seq = 0;
|
||||
}
|
||||
|
||||
/* Reset flags */
|
||||
((u_int8_t *)tcph)[13] = 0;
|
||||
tcph->rst = 1;
|
||||
tcph->ack = needs_ack;
|
||||
tcph->window = 0;
|
||||
tcph->urg_ptr = 0;
|
||||
tcph->check = 0;
|
||||
|
||||
/* Adjust TCP checksum */
|
||||
tcph->check = csum_ipv6_magic(&ipv6_hdr(nskb)->saddr,
|
||||
&ipv6_hdr(nskb)->daddr,
|
||||
sizeof(struct tcphdr), IPPROTO_TCP,
|
||||
csum_partial(tcph,
|
||||
sizeof(struct tcphdr), 0));
|
||||
}
|
||||
EXPORT_SYMBOL_GPL(nf_reject_ip6_tcphdr_put);
|
||||
|
||||
void nf_send_reset6(struct net *net, struct sk_buff *oldskb, int hook)
|
||||
{
|
||||
struct sk_buff *nskb;
|
||||
struct tcphdr otcph, *tcph;
|
||||
struct tcphdr _otcph;
|
||||
const struct tcphdr *otcph;
|
||||
unsigned int otcplen, hh_len;
|
||||
int tcphoff, needs_ack;
|
||||
const struct ipv6hdr *oip6h = ipv6_hdr(oldskb);
|
||||
struct ipv6hdr *ip6h;
|
||||
#define DEFAULT_TOS_VALUE 0x0U
|
||||
const __u8 tclass = DEFAULT_TOS_VALUE;
|
||||
struct dst_entry *dst = NULL;
|
||||
u8 proto;
|
||||
__be16 frag_off;
|
||||
struct flowi6 fl6;
|
||||
|
||||
if ((!(ipv6_addr_type(&oip6h->saddr) & IPV6_ADDR_UNICAST)) ||
|
||||
|
|
@ -34,45 +145,16 @@ void nf_send_reset6(struct net *net, struct sk_buff *oldskb, int hook)
|
|||
return;
|
||||
}
|
||||
|
||||
proto = oip6h->nexthdr;
|
||||
tcphoff = ipv6_skip_exthdr(oldskb, ((u8*)(oip6h+1) - oldskb->data), &proto, &frag_off);
|
||||
|
||||
if ((tcphoff < 0) || (tcphoff > oldskb->len)) {
|
||||
pr_debug("Cannot get TCP header.\n");
|
||||
otcph = nf_reject_ip6_tcphdr_get(oldskb, &_otcph, &otcplen, hook);
|
||||
if (!otcph)
|
||||
return;
|
||||
}
|
||||
|
||||
otcplen = oldskb->len - tcphoff;
|
||||
|
||||
/* IP header checks: fragment, too short. */
|
||||
if (proto != IPPROTO_TCP || otcplen < sizeof(struct tcphdr)) {
|
||||
pr_debug("proto(%d) != IPPROTO_TCP, "
|
||||
"or too short. otcplen = %d\n",
|
||||
proto, otcplen);
|
||||
return;
|
||||
}
|
||||
|
||||
if (skb_copy_bits(oldskb, tcphoff, &otcph, sizeof(struct tcphdr)))
|
||||
BUG();
|
||||
|
||||
/* No RST for RST. */
|
||||
if (otcph.rst) {
|
||||
pr_debug("RST is set\n");
|
||||
return;
|
||||
}
|
||||
|
||||
/* Check checksum. */
|
||||
if (nf_ip6_checksum(oldskb, hook, tcphoff, IPPROTO_TCP)) {
|
||||
pr_debug("TCP checksum is invalid\n");
|
||||
return;
|
||||
}
|
||||
|
||||
memset(&fl6, 0, sizeof(fl6));
|
||||
fl6.flowi6_proto = IPPROTO_TCP;
|
||||
fl6.saddr = oip6h->daddr;
|
||||
fl6.daddr = oip6h->saddr;
|
||||
fl6.fl6_sport = otcph.dest;
|
||||
fl6.fl6_dport = otcph.source;
|
||||
fl6.fl6_sport = otcph->dest;
|
||||
fl6.fl6_dport = otcph->source;
|
||||
security_skb_classify_flow(oldskb, flowi6_to_flowi(&fl6));
|
||||
dst = ip6_route_output(net, NULL, &fl6);
|
||||
if (dst == NULL || dst->error) {
|
||||
|
|
@ -97,48 +179,9 @@ void nf_send_reset6(struct net *net, struct sk_buff *oldskb, int hook)
|
|||
skb_dst_set(nskb, dst);
|
||||
|
||||
skb_reserve(nskb, hh_len + dst->header_len);
|
||||
|
||||
skb_put(nskb, sizeof(struct ipv6hdr));
|
||||
skb_reset_network_header(nskb);
|
||||
ip6h = ipv6_hdr(nskb);
|
||||
ip6_flow_hdr(ip6h, tclass, 0);
|
||||
ip6h->hop_limit = ip6_dst_hoplimit(dst);
|
||||
ip6h->nexthdr = IPPROTO_TCP;
|
||||
ip6h->saddr = oip6h->daddr;
|
||||
ip6h->daddr = oip6h->saddr;
|
||||
|
||||
skb_reset_transport_header(nskb);
|
||||
tcph = (struct tcphdr *)skb_put(nskb, sizeof(struct tcphdr));
|
||||
/* Truncate to length (no data) */
|
||||
tcph->doff = sizeof(struct tcphdr)/4;
|
||||
tcph->source = otcph.dest;
|
||||
tcph->dest = otcph.source;
|
||||
|
||||
if (otcph.ack) {
|
||||
needs_ack = 0;
|
||||
tcph->seq = otcph.ack_seq;
|
||||
tcph->ack_seq = 0;
|
||||
} else {
|
||||
needs_ack = 1;
|
||||
tcph->ack_seq = htonl(ntohl(otcph.seq) + otcph.syn + otcph.fin
|
||||
+ otcplen - (otcph.doff<<2));
|
||||
tcph->seq = 0;
|
||||
}
|
||||
|
||||
/* Reset flags */
|
||||
((u_int8_t *)tcph)[13] = 0;
|
||||
tcph->rst = 1;
|
||||
tcph->ack = needs_ack;
|
||||
tcph->window = 0;
|
||||
tcph->urg_ptr = 0;
|
||||
tcph->check = 0;
|
||||
|
||||
/* Adjust TCP checksum */
|
||||
tcph->check = csum_ipv6_magic(&ipv6_hdr(nskb)->saddr,
|
||||
&ipv6_hdr(nskb)->daddr,
|
||||
sizeof(struct tcphdr), IPPROTO_TCP,
|
||||
csum_partial(tcph,
|
||||
sizeof(struct tcphdr), 0));
|
||||
ip6h = nf_reject_ip6hdr_put(nskb, oldskb, IPPROTO_TCP,
|
||||
ip6_dst_hoplimit(dst));
|
||||
nf_reject_ip6_tcphdr_put(nskb, oldskb, otcph, otcplen);
|
||||
|
||||
nf_ct_attach(nskb, oldskb);
|
||||
|
||||
|
|
|
|||
Loading…
Reference in New Issue