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Date: Fri, 31 Oct 2014 13:18:30 +0100
From: Pablo Neira Ayuso <pablo@...filter.org>
To: netfilter-devel@...r.kernel.org
Cc: davem@...emloft.net, netdev@...r.kernel.org
Subject: [PATCH 4/6] 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@...filter.org>
---
include/net/netfilter/ipv6/nf_reject.h | 10 ++
net/ipv6/netfilter/nf_reject_ipv6.c | 175 ++++++++++++++++++++------------
2 files changed, 119 insertions(+), 66 deletions(-)
diff --git a/include/net/netfilter/ipv6/nf_reject.h b/include/net/netfilter/ipv6/nf_reject.h
index 48e1881..23216d4 100644
--- a/include/net/netfilter/ipv6/nf_reject.h
+++ b/include/net/netfilter/ipv6/nf_reject.h
@@ -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 */
diff --git a/net/ipv6/netfilter/nf_reject_ipv6.c b/net/ipv6/netfilter/nf_reject_ipv6.c
index 20d9def..015eb8a 100644
--- a/net/ipv6/netfilter/nf_reject_ipv6.c
+++ b/net/ipv6/netfilter/nf_reject_ipv6.c
@@ -12,116 +12,102 @@
#include <net/ip6_fib.h>
#include <net/ip6_checksum.h>
#include <linux/netfilter_ipv6.h>
+#include <net/netfilter/ipv6/nf_reject.h>
-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 sk_buff *nskb;
- struct tcphdr otcph, *tcph;
- 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)) ||
- (!(ipv6_addr_type(&oip6h->daddr) & IPV6_ADDR_UNICAST))) {
- pr_debug("addr is not unicast.\n");
- return;
- }
+ int tcphoff;
proto = oip6h->nexthdr;
- tcphoff = ipv6_skip_exthdr(oldskb, ((u8*)(oip6h+1) - oldskb->data), &proto, &frag_off);
+ 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;
+ return NULL;
}
- otcplen = oldskb->len - tcphoff;
+ *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 (proto != IPPROTO_TCP || *otcplen < sizeof(struct tcphdr)) {
+ pr_debug("proto(%d) != IPPROTO_TCP or too short (len = %d)\n",
+ proto, *otcplen);
+ return NULL;
}
- if (skb_copy_bits(oldskb, tcphoff, &otcph, sizeof(struct tcphdr)))
- BUG();
+ otcph = skb_header_pointer(oldskb, tcphoff, sizeof(struct tcphdr),
+ otcph);
+ if (otcph == NULL)
+ return NULL;
/* No RST for RST. */
- if (otcph.rst) {
+ if (otcph->rst) {
pr_debug("RST is set\n");
- return;
+ return NULL;
}
/* 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;
- security_skb_classify_flow(oldskb, flowi6_to_flowi(&fl6));
- dst = ip6_route_output(net, NULL, &fl6);
- if (dst == NULL || dst->error) {
- dst_release(dst);
- return;
- }
- dst = xfrm_lookup(net, dst, flowi6_to_flowi(&fl6), NULL, 0);
- if (IS_ERR(dst))
- return;
-
- hh_len = (dst->dev->hard_header_len + 15)&~15;
- nskb = alloc_skb(hh_len + 15 + dst->header_len + sizeof(struct ipv6hdr)
- + sizeof(struct tcphdr) + dst->trailer_len,
- GFP_ATOMIC);
-
- if (!nskb) {
- net_dbg_ratelimited("cannot alloc skb\n");
- dst_release(dst);
- return;
+ return NULL;
}
- skb_dst_set(nskb, dst);
+ return otcph;
+}
+EXPORT_SYMBOL_GPL(nf_reject_ip6_tcphdr_get);
- skb_reserve(nskb, hh_len + dst->header_len);
+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 = ip6_dst_hoplimit(dst);
- ip6h->nexthdr = IPPROTO_TCP;
+ 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 = otcph.dest;
- tcph->dest = otcph.source;
+ tcph->source = oth->dest;
+ tcph->dest = oth->source;
- if (otcph.ack) {
+ if (oth->ack) {
needs_ack = 0;
- tcph->seq = otcph.ack_seq;
+ tcph->seq = oth->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->ack_seq = htonl(ntohl(oth->seq) + oth->syn + oth->fin +
+ otcplen - (oth->doff<<2));
tcph->seq = 0;
}
@@ -139,6 +125,63 @@ void nf_send_reset6(struct net *net, struct sk_buff *oldskb, int hook)
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;
+ const struct tcphdr *otcph;
+ unsigned int otcplen, hh_len;
+ const struct ipv6hdr *oip6h = ipv6_hdr(oldskb);
+ struct ipv6hdr *ip6h;
+ struct dst_entry *dst = NULL;
+ struct flowi6 fl6;
+
+ if ((!(ipv6_addr_type(&oip6h->saddr) & IPV6_ADDR_UNICAST)) ||
+ (!(ipv6_addr_type(&oip6h->daddr) & IPV6_ADDR_UNICAST))) {
+ pr_debug("addr is not unicast.\n");
+ return;
+ }
+
+ otcph = nf_reject_ip6_tcphdr_get(oldskb, &_otcph, &otcplen, hook);
+ if (!otcph)
+ 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;
+ security_skb_classify_flow(oldskb, flowi6_to_flowi(&fl6));
+ dst = ip6_route_output(net, NULL, &fl6);
+ if (dst == NULL || dst->error) {
+ dst_release(dst);
+ return;
+ }
+ dst = xfrm_lookup(net, dst, flowi6_to_flowi(&fl6), NULL, 0);
+ if (IS_ERR(dst))
+ return;
+
+ hh_len = (dst->dev->hard_header_len + 15)&~15;
+ nskb = alloc_skb(hh_len + 15 + dst->header_len + sizeof(struct ipv6hdr)
+ + sizeof(struct tcphdr) + dst->trailer_len,
+ GFP_ATOMIC);
+
+ if (!nskb) {
+ net_dbg_ratelimited("cannot alloc skb\n");
+ dst_release(dst);
+ return;
+ }
+
+ skb_dst_set(nskb, dst);
+
+ skb_reserve(nskb, hh_len + dst->header_len);
+ 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);
--
1.7.10.4
--
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