0c4b51f005
This is immediately motivated by the bridge code that chains functions that call into netfilter. Without passing net into the okfns the bridge code would need to guess about the best expression for the network namespace to process packets in. As net is frequently one of the first things computed in continuation functions after netfilter has done it's job passing in the desired network namespace is in many cases a code simplification. To support this change the function dst_output_okfn is introduced to simplify passing dst_output as an okfn. For the moment dst_output_okfn just silently drops the struct net. Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com> Signed-off-by: David S. Miller <davem@davemloft.net>
167 lines
3.9 KiB
C
167 lines
3.9 KiB
C
/*
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* INET An implementation of the TCP/IP protocol suite for the LINUX
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* operating system. INET is implemented using the BSD Socket
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* interface as the means of communication with the user level.
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*
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* The IP forwarding functionality.
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*
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* Authors: see ip.c
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*
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* Fixes:
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* Many : Split from ip.c , see ip_input.c for
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* history.
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* Dave Gregorich : NULL ip_rt_put fix for multicast
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* routing.
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* Jos Vos : Add call_out_firewall before sending,
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* use output device for accounting.
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* Jos Vos : Call forward firewall after routing
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* (always use output device).
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* Mike McLagan : Routing by source
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*/
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#include <linux/types.h>
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#include <linux/mm.h>
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#include <linux/skbuff.h>
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#include <linux/ip.h>
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#include <linux/icmp.h>
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#include <linux/netdevice.h>
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#include <linux/slab.h>
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#include <net/sock.h>
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#include <net/ip.h>
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#include <net/tcp.h>
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#include <net/udp.h>
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#include <net/icmp.h>
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#include <linux/tcp.h>
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#include <linux/udp.h>
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#include <linux/netfilter_ipv4.h>
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#include <net/checksum.h>
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#include <linux/route.h>
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#include <net/route.h>
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#include <net/xfrm.h>
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static bool ip_exceeds_mtu(const struct sk_buff *skb, unsigned int mtu)
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{
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if (skb->len <= mtu)
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return false;
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if (unlikely((ip_hdr(skb)->frag_off & htons(IP_DF)) == 0))
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return false;
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/* original fragment exceeds mtu and DF is set */
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if (unlikely(IPCB(skb)->frag_max_size > mtu))
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return true;
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if (skb->ignore_df)
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return false;
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if (skb_is_gso(skb) && skb_gso_network_seglen(skb) <= mtu)
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return false;
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return true;
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}
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static int ip_forward_finish(struct net *net, struct sock *sk, struct sk_buff *skb)
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{
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struct ip_options *opt = &(IPCB(skb)->opt);
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IP_INC_STATS_BH(net, IPSTATS_MIB_OUTFORWDATAGRAMS);
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IP_ADD_STATS_BH(net, IPSTATS_MIB_OUTOCTETS, skb->len);
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if (unlikely(opt->optlen))
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ip_forward_options(skb);
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skb_sender_cpu_clear(skb);
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return dst_output(sk, skb);
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}
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int ip_forward(struct sk_buff *skb)
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{
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u32 mtu;
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struct iphdr *iph; /* Our header */
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struct rtable *rt; /* Route we use */
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struct ip_options *opt = &(IPCB(skb)->opt);
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struct net *net;
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/* that should never happen */
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if (skb->pkt_type != PACKET_HOST)
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goto drop;
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if (unlikely(skb->sk))
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goto drop;
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if (skb_warn_if_lro(skb))
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goto drop;
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if (!xfrm4_policy_check(NULL, XFRM_POLICY_FWD, skb))
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goto drop;
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if (IPCB(skb)->opt.router_alert && ip_call_ra_chain(skb))
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return NET_RX_SUCCESS;
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skb_forward_csum(skb);
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net = dev_net(skb->dev);
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/*
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* According to the RFC, we must first decrease the TTL field. If
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* that reaches zero, we must reply an ICMP control message telling
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* that the packet's lifetime expired.
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*/
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if (ip_hdr(skb)->ttl <= 1)
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goto too_many_hops;
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if (!xfrm4_route_forward(skb))
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goto drop;
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rt = skb_rtable(skb);
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if (opt->is_strictroute && rt->rt_uses_gateway)
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goto sr_failed;
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IPCB(skb)->flags |= IPSKB_FORWARDED;
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mtu = ip_dst_mtu_maybe_forward(&rt->dst, true);
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if (ip_exceeds_mtu(skb, mtu)) {
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IP_INC_STATS(net, IPSTATS_MIB_FRAGFAILS);
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icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED,
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htonl(mtu));
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goto drop;
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}
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/* We are about to mangle packet. Copy it! */
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if (skb_cow(skb, LL_RESERVED_SPACE(rt->dst.dev)+rt->dst.header_len))
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goto drop;
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iph = ip_hdr(skb);
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/* Decrease ttl after skb cow done */
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ip_decrease_ttl(iph);
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/*
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* We now generate an ICMP HOST REDIRECT giving the route
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* we calculated.
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*/
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if (IPCB(skb)->flags & IPSKB_DOREDIRECT && !opt->srr &&
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!skb_sec_path(skb))
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ip_rt_send_redirect(skb);
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skb->priority = rt_tos2priority(iph->tos);
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return NF_HOOK(NFPROTO_IPV4, NF_INET_FORWARD,
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net, NULL, skb, skb->dev, rt->dst.dev,
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ip_forward_finish);
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sr_failed:
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/*
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* Strict routing permits no gatewaying
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*/
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icmp_send(skb, ICMP_DEST_UNREACH, ICMP_SR_FAILED, 0);
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goto drop;
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too_many_hops:
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/* Tell the sender its packet died... */
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IP_INC_STATS_BH(net, IPSTATS_MIB_INHDRERRORS);
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icmp_send(skb, ICMP_TIME_EXCEEDED, ICMP_EXC_TTL, 0);
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drop:
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kfree_skb(skb);
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return NET_RX_DROP;
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}
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