That can be reused by the reject bridge expression to build the reject
packet. The new functions are:
* nf_reject_ip_tcphdr_get(): to sanitize and to obtain the TCP header.
* nf_reject_iphdr_put(): to build the IPv4 header.
* nf_reject_ip_tcphdr_put(): to build the TCP header.
Signed-off-by: Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx>
---
include/net/netfilter/ipv4/nf_reject.h | 10 ++++
net/ipv4/netfilter/nf_reject_ipv4.c | 88 ++++++++++++++++++++++----------
2 files changed, 72 insertions(+), 26 deletions(-)
diff --git a/include/net/netfilter/ipv4/nf_reject.h b/include/net/netfilter/ipv4/nf_reject.h
index e842719..03e928a 100644
--- a/include/net/netfilter/ipv4/nf_reject.h
+++ b/include/net/netfilter/ipv4/nf_reject.h
@@ -1,6 +1,8 @@
#ifndef _IPV4_NF_REJECT_H
#define _IPV4_NF_REJECT_H
+#include <linux/skbuff.h>
+#include <net/ip.h>
#include <net/icmp.h>
static inline void nf_send_unreach(struct sk_buff *skb_in, int code)
@@ -10,4 +12,12 @@ static inline void nf_send_unreach(struct sk_buff *skb_in, int code)
void nf_send_reset(struct sk_buff *oldskb, int hook);
+const struct tcphdr *nf_reject_ip_tcphdr_get(struct sk_buff *oldskb,
+ struct tcphdr *_oth, int hook);
+struct iphdr *nf_reject_iphdr_put(struct sk_buff *nskb,
+ const struct sk_buff *oldskb,
+ __be16 protocol, int ttl);
+void nf_reject_ip_tcphdr_put(struct sk_buff *nskb, const struct sk_buff *oldskb,
+ const struct tcphdr *oth);
+
#endif /* _IPV4_NF_REJECT_H */
diff --git a/net/ipv4/netfilter/nf_reject_ipv4.c b/net/ipv4/netfilter/nf_reject_ipv4.c
index 92b303d..9813440 100644
--- a/net/ipv4/netfilter/nf_reject_ipv4.c
+++ b/net/ipv4/netfilter/nf_reject_ipv4.c
@@ -13,42 +13,37 @@
#include <net/dst.h>
#include <linux/netfilter_ipv4.h>
-/* Send RST reply */
-void nf_send_reset(struct sk_buff *oldskb, int hook)
+const struct tcphdr *nf_reject_ip_tcphdr_get(struct sk_buff *oldskb,
+ struct tcphdr *_oth, int hook)
{
- struct sk_buff *nskb;
- const struct iphdr *oiph;
- struct iphdr *niph;
const struct tcphdr *oth;
- struct tcphdr _otcph, *tcph;
/* IP header checks: fragment. */
if (ip_hdr(oldskb)->frag_off & htons(IP_OFFSET))
- return;
+ return NULL;
oth = skb_header_pointer(oldskb, ip_hdrlen(oldskb),
- sizeof(_otcph), &_otcph);
+ sizeof(struct tcphdr), _oth);
if (oth == NULL)
- return;
+ return NULL;
/* No RST for RST. */
if (oth->rst)
- return;
-
- if (skb_rtable(oldskb)->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST))
- return;
+ return NULL;
/* Check checksum */
if (nf_ip_checksum(oldskb, hook, ip_hdrlen(oldskb), IPPROTO_TCP))
- return;
- oiph = ip_hdr(oldskb);
+ return NULL;
- nskb = alloc_skb(sizeof(struct iphdr) + sizeof(struct tcphdr) +
- LL_MAX_HEADER, GFP_ATOMIC);
- if (!nskb)
- return;
+ return oth;
+}
+EXPORT_SYMBOL_GPL(nf_reject_ip_tcphdr_get);
- skb_reserve(nskb, LL_MAX_HEADER);
+struct iphdr *nf_reject_iphdr_put(struct sk_buff *nskb,
+ const struct sk_buff *oldskb,
+ __be16 protocol, int ttl)
+{
+ struct iphdr *niph, *oiph = ip_hdr(oldskb);
skb_reset_network_header(nskb);
niph = (struct iphdr *)skb_put(nskb, sizeof(struct iphdr));
@@ -57,10 +52,23 @@ void nf_send_reset(struct sk_buff *oldskb, int hook)
niph->tos = 0;
niph->id = 0;
niph->frag_off = htons(IP_DF);
- niph->protocol = IPPROTO_TCP;
+ niph->protocol = protocol;
niph->check = 0;
niph->saddr = oiph->daddr;
niph->daddr = oiph->saddr;
+ niph->ttl = ttl;
+
+ nskb->protocol = htons(ETH_P_IP);
+
+ return niph;
+}
+EXPORT_SYMBOL_GPL(nf_reject_iphdr_put);
+
+void nf_reject_ip_tcphdr_put(struct sk_buff *nskb, const struct sk_buff *oldskb,
+ const struct tcphdr *oth)
+{
+ struct iphdr *niph = ip_hdr(nskb);
+ struct tcphdr *tcph;
skb_reset_transport_header(nskb);
tcph = (struct tcphdr *)skb_put(nskb, sizeof(struct tcphdr));
@@ -69,9 +77,9 @@ void nf_send_reset(struct sk_buff *oldskb, int hook)
tcph->dest = oth->source;
tcph->doff = sizeof(struct tcphdr) / 4;
- if (oth->ack)
+ if (oth->ack) {
tcph->seq = oth->ack_seq;
- else {
+ } else {
tcph->ack_seq = htonl(ntohl(oth->seq) + oth->syn + oth->fin +
oldskb->len - ip_hdrlen(oldskb) -
(oth->doff << 2));
@@ -84,16 +92,44 @@ void nf_send_reset(struct sk_buff *oldskb, int hook)
nskb->ip_summed = CHECKSUM_PARTIAL;
nskb->csum_start = (unsigned char *)tcph - nskb->head;
nskb->csum_offset = offsetof(struct tcphdr, check);
+}
+EXPORT_SYMBOL_GPL(nf_reject_ip_tcphdr_put);
+
+/* Send RST reply */
+void nf_send_reset(struct sk_buff *oldskb, int hook)
+{
+ struct sk_buff *nskb;
+ const struct iphdr *oiph;
+ struct iphdr *niph;
+ const struct tcphdr *oth;
+ struct tcphdr _oth;
+
+ oth = nf_reject_ip_tcphdr_get(oldskb, &_oth, hook);
+ if (!oth)
+ return;
+
+ if (skb_rtable(oldskb)->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST))
+ return;
+
+ oiph = ip_hdr(oldskb);
+
+ nskb = alloc_skb(sizeof(struct iphdr) + sizeof(struct tcphdr) +
+ LL_MAX_HEADER, GFP_ATOMIC);
+ if (!nskb)
+ return;
+
+ skb_reserve(nskb, LL_MAX_HEADER);
+
+ niph = nf_reject_iphdr_put(nskb, oldskb, IPPROTO_TCP,
+ ip4_dst_hoplimit(skb_dst(nskb)));
+ nf_reject_ip_tcphdr_put(nskb, oldskb, oth);
/* ip_route_me_harder expects skb->dst to be set */
skb_dst_set_noref(nskb, skb_dst(oldskb));
- nskb->protocol = htons(ETH_P_IP);
if (ip_route_me_harder(nskb, RTN_UNSPEC))
goto free_nskb;
- niph->ttl = ip4_dst_hoplimit(skb_dst(nskb));
-
/* "Never happens" */
if (nskb->len > dst_mtu(skb_dst(nskb)))
goto free_nskb;
--
1.7.10.4
--
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