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-rw-r--r--net/ipv4/ip_forward.c159
1 files changed, 159 insertions, 0 deletions
diff --git a/net/ipv4/ip_forward.c b/net/ipv4/ip_forward.c
new file mode 100644
index 000000000..367448494
--- /dev/null
+++ b/net/ipv4/ip_forward.c
@@ -0,0 +1,159 @@
+/*
+ * INET An implementation of the TCP/IP protocol suite for the LINUX
+ * operating system. INET is implemented using the BSD Socket
+ * interface as the means of communication with the user level.
+ *
+ * The IP forwarding functionality.
+ *
+ * Authors: see ip.c
+ *
+ * Fixes:
+ * Many : Split from ip.c , see ip_input.c for
+ * history.
+ * Dave Gregorich : NULL ip_rt_put fix for multicast
+ * routing.
+ * Jos Vos : Add call_out_firewall before sending,
+ * use output device for accounting.
+ * Jos Vos : Call forward firewall after routing
+ * (always use output device).
+ * Mike McLagan : Routing by source
+ */
+
+#include <linux/types.h>
+#include <linux/mm.h>
+#include <linux/skbuff.h>
+#include <linux/ip.h>
+#include <linux/icmp.h>
+#include <linux/netdevice.h>
+#include <linux/slab.h>
+#include <net/sock.h>
+#include <net/ip.h>
+#include <net/tcp.h>
+#include <net/udp.h>
+#include <net/icmp.h>
+#include <linux/tcp.h>
+#include <linux/udp.h>
+#include <linux/netfilter_ipv4.h>
+#include <net/checksum.h>
+#include <linux/route.h>
+#include <net/route.h>
+#include <net/xfrm.h>
+
+static bool ip_may_fragment(const struct sk_buff *skb)
+{
+ return unlikely((ip_hdr(skb)->frag_off & htons(IP_DF)) == 0) ||
+ skb->ignore_df;
+}
+
+static bool ip_exceeds_mtu(const struct sk_buff *skb, unsigned int mtu)
+{
+ if (skb->len <= mtu)
+ return false;
+
+ if (skb_is_gso(skb) && skb_gso_network_seglen(skb) <= mtu)
+ return false;
+
+ return true;
+}
+
+
+static int ip_forward_finish(struct sock *sk, struct sk_buff *skb)
+{
+ struct ip_options *opt = &(IPCB(skb)->opt);
+
+ IP_INC_STATS_BH(dev_net(skb_dst(skb)->dev), IPSTATS_MIB_OUTFORWDATAGRAMS);
+ IP_ADD_STATS_BH(dev_net(skb_dst(skb)->dev), IPSTATS_MIB_OUTOCTETS, skb->len);
+
+ if (unlikely(opt->optlen))
+ ip_forward_options(skb);
+
+ skb_sender_cpu_clear(skb);
+ return dst_output_sk(sk, skb);
+}
+
+int ip_forward(struct sk_buff *skb)
+{
+ u32 mtu;
+ struct iphdr *iph; /* Our header */
+ struct rtable *rt; /* Route we use */
+ struct ip_options *opt = &(IPCB(skb)->opt);
+
+ /* that should never happen */
+ if (skb->pkt_type != PACKET_HOST)
+ goto drop;
+
+ if (unlikely(skb->sk))
+ goto drop;
+
+ if (skb_warn_if_lro(skb))
+ goto drop;
+
+ if (!xfrm4_policy_check(NULL, XFRM_POLICY_FWD, skb))
+ goto drop;
+
+ if (IPCB(skb)->opt.router_alert && ip_call_ra_chain(skb))
+ return NET_RX_SUCCESS;
+
+ skb_forward_csum(skb);
+
+ /*
+ * According to the RFC, we must first decrease the TTL field. If
+ * that reaches zero, we must reply an ICMP control message telling
+ * that the packet's lifetime expired.
+ */
+ if (ip_hdr(skb)->ttl <= 1)
+ goto too_many_hops;
+
+ if (!xfrm4_route_forward(skb))
+ goto drop;
+
+ rt = skb_rtable(skb);
+
+ if (opt->is_strictroute && rt->rt_uses_gateway)
+ goto sr_failed;
+
+ IPCB(skb)->flags |= IPSKB_FORWARDED;
+ mtu = ip_dst_mtu_maybe_forward(&rt->dst, true);
+ if (!ip_may_fragment(skb) && ip_exceeds_mtu(skb, mtu)) {
+ IP_INC_STATS(dev_net(rt->dst.dev), IPSTATS_MIB_FRAGFAILS);
+ icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED,
+ htonl(mtu));
+ goto drop;
+ }
+
+ /* We are about to mangle packet. Copy it! */
+ if (skb_cow(skb, LL_RESERVED_SPACE(rt->dst.dev)+rt->dst.header_len))
+ goto drop;
+ iph = ip_hdr(skb);
+
+ /* Decrease ttl after skb cow done */
+ ip_decrease_ttl(iph);
+
+ /*
+ * We now generate an ICMP HOST REDIRECT giving the route
+ * we calculated.
+ */
+ if (IPCB(skb)->flags & IPSKB_DOREDIRECT && !opt->srr &&
+ !skb_sec_path(skb))
+ ip_rt_send_redirect(skb);
+
+ skb->priority = rt_tos2priority(iph->tos);
+
+ return NF_HOOK(NFPROTO_IPV4, NF_INET_FORWARD, NULL, skb,
+ skb->dev, rt->dst.dev, ip_forward_finish);
+
+sr_failed:
+ /*
+ * Strict routing permits no gatewaying
+ */
+ icmp_send(skb, ICMP_DEST_UNREACH, ICMP_SR_FAILED, 0);
+ goto drop;
+
+too_many_hops:
+ /* Tell the sender its packet died... */
+ IP_INC_STATS_BH(dev_net(skb_dst(skb)->dev), IPSTATS_MIB_INHDRERRORS);
+ icmp_send(skb, ICMP_TIME_EXCEEDED, ICMP_EXC_TTL, 0);
+drop:
+ kfree_skb(skb);
+ return NET_RX_DROP;
+}