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>

diff --git a/include/net/netfilter/ipv6/nf_reject.h b/include/net/netfilter/ipv6/nf_reject.h
index 48e1881..23216d4 100644 (file)
--- 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 (file)
--- 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);