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c7ba65d7b6
Doing the segmentation in the forward path has one major drawback:
When using virtio, we may process gso udp packets coming
from host network stack. In that case, netfilter POSTROUTING
will see one packet with udp header followed by multiple ip
fragments.
Delay the segmentation and do it after POSTROUTING invocation
to avoid this.
Fixes: fe6cc55f3a ("net: ip, ipv6: handle gso skbs in forwarding path")
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
155 lines
3.7 KiB
C
155 lines
3.7 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_may_fragment(const struct sk_buff *skb)
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{
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return unlikely((ip_hdr(skb)->frag_off & htons(IP_DF)) == 0) ||
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skb->local_df;
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}
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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 (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 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(dev_net(skb_dst(skb)->dev), IPSTATS_MIB_OUTFORWDATAGRAMS);
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IP_ADD_STATS_BH(dev_net(skb_dst(skb)->dev), 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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return dst_output(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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/* 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 (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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/*
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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_may_fragment(skb) && ip_exceeds_mtu(skb, mtu)) {
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IP_INC_STATS(dev_net(rt->dst.dev), 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 (rt->rt_flags&RTCF_DOREDIRECT && !opt->srr && !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, skb, skb->dev,
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rt->dst.dev, 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(dev_net(skb_dst(skb)->dev), 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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