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dd87147eed
This patch adds the flag XFRM_STATE_NOPMTUDISC for xfrm states. It is similar to the nopmtudisc on IPIP/GRE tunnels. It only has an effect on IPv4 tunnel mode states. For these states, it will ensure that the DF flag is always cleared. This is primarily useful to work around ICMP blackholes. In future this flag could also allow a larger MTU to be set within the tunnel just like IPIP/GRE tunnels. This could be useful for short haul tunnels where temporary fragmentation outside the tunnel is desired over smaller fragments inside the tunnel. Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au> Acked-by: James Morris <jmorris@redhat.com> Signed-off-by: David S. Miller <davem@davemloft.net>
146 lines
3.1 KiB
C
146 lines
3.1 KiB
C
/*
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* xfrm4_output.c - Common IPsec encapsulation code for IPv4.
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* Copyright (c) 2004 Herbert Xu <herbert@gondor.apana.org.au>
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*/
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#include <linux/skbuff.h>
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#include <linux/spinlock.h>
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#include <net/inet_ecn.h>
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#include <net/ip.h>
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#include <net/xfrm.h>
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#include <net/icmp.h>
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/* Add encapsulation header.
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*
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* In transport mode, the IP header will be moved forward to make space
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* for the encapsulation header.
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*
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* In tunnel mode, the top IP header will be constructed per RFC 2401.
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* The following fields in it shall be filled in by x->type->output:
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* tot_len
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* check
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*
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* On exit, skb->h will be set to the start of the payload to be processed
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* by x->type->output and skb->nh will be set to the top IP header.
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*/
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static void xfrm4_encap(struct sk_buff *skb)
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{
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struct dst_entry *dst = skb->dst;
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struct xfrm_state *x = dst->xfrm;
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struct iphdr *iph, *top_iph;
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int flags;
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iph = skb->nh.iph;
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skb->h.ipiph = iph;
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skb->nh.raw = skb_push(skb, x->props.header_len);
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top_iph = skb->nh.iph;
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if (!x->props.mode) {
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skb->h.raw += iph->ihl*4;
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memmove(top_iph, iph, iph->ihl*4);
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return;
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}
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top_iph->ihl = 5;
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top_iph->version = 4;
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/* DS disclosed */
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top_iph->tos = INET_ECN_encapsulate(iph->tos, iph->tos);
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flags = x->props.flags;
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if (flags & XFRM_STATE_NOECN)
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IP_ECN_clear(top_iph);
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top_iph->frag_off = (flags & XFRM_STATE_NOPMTUDISC) ?
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0 : (iph->frag_off & htons(IP_DF));
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if (!top_iph->frag_off)
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__ip_select_ident(top_iph, dst, 0);
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top_iph->ttl = dst_metric(dst->child, RTAX_HOPLIMIT);
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top_iph->saddr = x->props.saddr.a4;
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top_iph->daddr = x->id.daddr.a4;
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top_iph->protocol = IPPROTO_IPIP;
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memset(&(IPCB(skb)->opt), 0, sizeof(struct ip_options));
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}
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static int xfrm4_tunnel_check_size(struct sk_buff *skb)
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{
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int mtu, ret = 0;
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struct dst_entry *dst;
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struct iphdr *iph = skb->nh.iph;
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if (IPCB(skb)->flags & IPSKB_XFRM_TUNNEL_SIZE)
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goto out;
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IPCB(skb)->flags |= IPSKB_XFRM_TUNNEL_SIZE;
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if (!(iph->frag_off & htons(IP_DF)) || skb->local_df)
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goto out;
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dst = skb->dst;
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mtu = dst_mtu(dst);
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if (skb->len > mtu) {
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icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED, htonl(mtu));
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ret = -EMSGSIZE;
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}
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out:
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return ret;
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}
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int xfrm4_output(struct sk_buff *skb)
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{
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struct dst_entry *dst = skb->dst;
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struct xfrm_state *x = dst->xfrm;
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int err;
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if (skb->ip_summed == CHECKSUM_HW) {
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err = skb_checksum_help(skb, 0);
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if (err)
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goto error_nolock;
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}
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if (x->props.mode) {
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err = xfrm4_tunnel_check_size(skb);
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if (err)
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goto error_nolock;
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}
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spin_lock_bh(&x->lock);
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err = xfrm_state_check(x, skb);
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if (err)
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goto error;
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xfrm4_encap(skb);
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err = x->type->output(x, skb);
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if (err)
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goto error;
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x->curlft.bytes += skb->len;
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x->curlft.packets++;
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spin_unlock_bh(&x->lock);
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if (!(skb->dst = dst_pop(dst))) {
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err = -EHOSTUNREACH;
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goto error_nolock;
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}
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err = NET_XMIT_BYPASS;
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out_exit:
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return err;
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error:
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spin_unlock_bh(&x->lock);
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error_nolock:
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kfree_skb(skb);
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goto out_exit;
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}
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