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https://github.com/torvalds/linux
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73f156a6e8
Ideally, we would need to generate IP ID using a per destination IP generator. linux kernels used inet_peer cache for this purpose, but this had a huge cost on servers disabling MTU discovery. 1) each inet_peer struct consumes 192 bytes 2) inetpeer cache uses a binary tree of inet_peer structs, with a nominal size of ~66000 elements under load. 3) lookups in this tree are hitting a lot of cache lines, as tree depth is about 20. 4) If server deals with many tcp flows, we have a high probability of not finding the inet_peer, allocating a fresh one, inserting it in the tree with same initial ip_id_count, (cf secure_ip_id()) 5) We garbage collect inet_peer aggressively. IP ID generation do not have to be 'perfect' Goal is trying to avoid duplicates in a short period of time, so that reassembly units have a chance to complete reassembly of fragments belonging to one message before receiving other fragments with a recycled ID. We simply use an array of generators, and a Jenkin hash using the dst IP as a key. ipv6_select_ident() is put back into net/ipv6/ip6_output.c where it belongs (it is only used from this file) secure_ip_id() and secure_ipv6_id() no longer are needed. Rename ip_select_ident_more() to ip_select_ident_segs() to avoid unnecessary decrement/increment of the number of segments. Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
125 lines
2.9 KiB
C
125 lines
2.9 KiB
C
/*
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* xfrm4_mode_tunnel.c - Tunnel mode encapsulation for IPv4.
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*
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* Copyright (c) 2004-2006 Herbert Xu <herbert@gondor.apana.org.au>
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*/
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#include <linux/gfp.h>
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#include <linux/init.h>
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/skbuff.h>
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#include <linux/stringify.h>
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#include <net/dst.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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static inline void ipip_ecn_decapsulate(struct sk_buff *skb)
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{
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struct iphdr *inner_iph = ipip_hdr(skb);
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if (INET_ECN_is_ce(XFRM_MODE_SKB_CB(skb)->tos))
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IP_ECN_set_ce(inner_iph);
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}
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/* Add encapsulation header.
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*
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* The top IP header will be constructed per RFC 2401.
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*/
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static int xfrm4_mode_tunnel_output(struct xfrm_state *x, struct sk_buff *skb)
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{
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struct dst_entry *dst = skb_dst(skb);
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struct iphdr *top_iph;
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int flags;
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skb_set_network_header(skb, -x->props.header_len);
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skb->mac_header = skb->network_header +
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offsetof(struct iphdr, protocol);
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skb->transport_header = skb->network_header + sizeof(*top_iph);
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top_iph = ip_hdr(skb);
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top_iph->ihl = 5;
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top_iph->version = 4;
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top_iph->protocol = xfrm_af2proto(skb_dst(skb)->ops->family);
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/* DS disclosing depends on XFRM_SA_XFLAG_DONT_ENCAP_DSCP */
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if (x->props.extra_flags & XFRM_SA_XFLAG_DONT_ENCAP_DSCP)
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top_iph->tos = 0;
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else
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top_iph->tos = XFRM_MODE_SKB_CB(skb)->tos;
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top_iph->tos = INET_ECN_encapsulate(top_iph->tos,
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XFRM_MODE_SKB_CB(skb)->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 : (XFRM_MODE_SKB_CB(skb)->frag_off & htons(IP_DF));
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top_iph->ttl = ip4_dst_hoplimit(dst->child);
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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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ip_select_ident(skb, NULL);
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return 0;
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}
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static int xfrm4_mode_tunnel_input(struct xfrm_state *x, struct sk_buff *skb)
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{
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int err = -EINVAL;
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if (XFRM_MODE_SKB_CB(skb)->protocol != IPPROTO_IPIP)
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goto out;
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if (!pskb_may_pull(skb, sizeof(struct iphdr)))
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goto out;
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err = skb_unclone(skb, GFP_ATOMIC);
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if (err)
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goto out;
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if (x->props.flags & XFRM_STATE_DECAP_DSCP)
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ipv4_copy_dscp(XFRM_MODE_SKB_CB(skb)->tos, ipip_hdr(skb));
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if (!(x->props.flags & XFRM_STATE_NOECN))
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ipip_ecn_decapsulate(skb);
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skb_reset_network_header(skb);
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skb_mac_header_rebuild(skb);
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err = 0;
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out:
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return err;
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}
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static struct xfrm_mode xfrm4_tunnel_mode = {
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.input2 = xfrm4_mode_tunnel_input,
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.input = xfrm_prepare_input,
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.output2 = xfrm4_mode_tunnel_output,
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.output = xfrm4_prepare_output,
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.owner = THIS_MODULE,
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.encap = XFRM_MODE_TUNNEL,
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.flags = XFRM_MODE_FLAG_TUNNEL,
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};
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static int __init xfrm4_mode_tunnel_init(void)
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{
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return xfrm_register_mode(&xfrm4_tunnel_mode, AF_INET);
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}
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static void __exit xfrm4_mode_tunnel_exit(void)
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{
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int err;
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err = xfrm_unregister_mode(&xfrm4_tunnel_mode, AF_INET);
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BUG_ON(err);
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}
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module_init(xfrm4_mode_tunnel_init);
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module_exit(xfrm4_mode_tunnel_exit);
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MODULE_LICENSE("GPL");
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MODULE_ALIAS_XFRM_MODE(AF_INET, XFRM_MODE_TUNNEL);
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