![Eric Dumazet](/assets/img/avatar_default.png)
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>
174 lines
4.1 KiB
C
174 lines
4.1 KiB
C
#include <linux/kernel.h>
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#include <linux/init.h>
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#include <linux/cryptohash.h>
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#include <linux/module.h>
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#include <linux/cache.h>
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#include <linux/random.h>
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#include <linux/hrtimer.h>
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#include <linux/ktime.h>
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#include <linux/string.h>
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#include <linux/net.h>
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#include <net/secure_seq.h>
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#if IS_ENABLED(CONFIG_IPV6) || IS_ENABLED(CONFIG_INET)
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#define NET_SECRET_SIZE (MD5_MESSAGE_BYTES / 4)
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static u32 net_secret[NET_SECRET_SIZE] ____cacheline_aligned;
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static __always_inline void net_secret_init(void)
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{
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net_get_random_once(net_secret, sizeof(net_secret));
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}
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#endif
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#ifdef CONFIG_INET
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static u32 seq_scale(u32 seq)
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{
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/*
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* As close as possible to RFC 793, which
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* suggests using a 250 kHz clock.
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* Further reading shows this assumes 2 Mb/s networks.
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* For 10 Mb/s Ethernet, a 1 MHz clock is appropriate.
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* For 10 Gb/s Ethernet, a 1 GHz clock should be ok, but
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* we also need to limit the resolution so that the u32 seq
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* overlaps less than one time per MSL (2 minutes).
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* Choosing a clock of 64 ns period is OK. (period of 274 s)
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*/
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return seq + (ktime_to_ns(ktime_get_real()) >> 6);
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}
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#endif
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#if IS_ENABLED(CONFIG_IPV6)
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__u32 secure_tcpv6_sequence_number(const __be32 *saddr, const __be32 *daddr,
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__be16 sport, __be16 dport)
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{
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u32 secret[MD5_MESSAGE_BYTES / 4];
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u32 hash[MD5_DIGEST_WORDS];
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u32 i;
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net_secret_init();
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memcpy(hash, saddr, 16);
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for (i = 0; i < 4; i++)
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secret[i] = net_secret[i] + (__force u32)daddr[i];
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secret[4] = net_secret[4] +
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(((__force u16)sport << 16) + (__force u16)dport);
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for (i = 5; i < MD5_MESSAGE_BYTES / 4; i++)
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secret[i] = net_secret[i];
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md5_transform(hash, secret);
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return seq_scale(hash[0]);
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}
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EXPORT_SYMBOL(secure_tcpv6_sequence_number);
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u32 secure_ipv6_port_ephemeral(const __be32 *saddr, const __be32 *daddr,
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__be16 dport)
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{
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u32 secret[MD5_MESSAGE_BYTES / 4];
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u32 hash[MD5_DIGEST_WORDS];
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u32 i;
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net_secret_init();
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memcpy(hash, saddr, 16);
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for (i = 0; i < 4; i++)
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secret[i] = net_secret[i] + (__force u32) daddr[i];
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secret[4] = net_secret[4] + (__force u32)dport;
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for (i = 5; i < MD5_MESSAGE_BYTES / 4; i++)
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secret[i] = net_secret[i];
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md5_transform(hash, secret);
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return hash[0];
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}
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EXPORT_SYMBOL(secure_ipv6_port_ephemeral);
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#endif
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#ifdef CONFIG_INET
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__u32 secure_tcp_sequence_number(__be32 saddr, __be32 daddr,
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__be16 sport, __be16 dport)
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{
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u32 hash[MD5_DIGEST_WORDS];
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net_secret_init();
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hash[0] = (__force u32)saddr;
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hash[1] = (__force u32)daddr;
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hash[2] = ((__force u16)sport << 16) + (__force u16)dport;
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hash[3] = net_secret[15];
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md5_transform(hash, net_secret);
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return seq_scale(hash[0]);
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}
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u32 secure_ipv4_port_ephemeral(__be32 saddr, __be32 daddr, __be16 dport)
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{
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u32 hash[MD5_DIGEST_WORDS];
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net_secret_init();
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hash[0] = (__force u32)saddr;
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hash[1] = (__force u32)daddr;
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hash[2] = (__force u32)dport ^ net_secret[14];
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hash[3] = net_secret[15];
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md5_transform(hash, net_secret);
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return hash[0];
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}
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EXPORT_SYMBOL_GPL(secure_ipv4_port_ephemeral);
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#endif
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#if IS_ENABLED(CONFIG_IP_DCCP)
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u64 secure_dccp_sequence_number(__be32 saddr, __be32 daddr,
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__be16 sport, __be16 dport)
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{
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u32 hash[MD5_DIGEST_WORDS];
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u64 seq;
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net_secret_init();
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hash[0] = (__force u32)saddr;
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hash[1] = (__force u32)daddr;
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hash[2] = ((__force u16)sport << 16) + (__force u16)dport;
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hash[3] = net_secret[15];
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md5_transform(hash, net_secret);
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seq = hash[0] | (((u64)hash[1]) << 32);
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seq += ktime_to_ns(ktime_get_real());
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seq &= (1ull << 48) - 1;
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return seq;
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}
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EXPORT_SYMBOL(secure_dccp_sequence_number);
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#if IS_ENABLED(CONFIG_IPV6)
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u64 secure_dccpv6_sequence_number(__be32 *saddr, __be32 *daddr,
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__be16 sport, __be16 dport)
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{
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u32 secret[MD5_MESSAGE_BYTES / 4];
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u32 hash[MD5_DIGEST_WORDS];
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u64 seq;
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u32 i;
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net_secret_init();
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memcpy(hash, saddr, 16);
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for (i = 0; i < 4; i++)
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secret[i] = net_secret[i] + daddr[i];
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secret[4] = net_secret[4] +
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(((__force u16)sport << 16) + (__force u16)dport);
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for (i = 5; i < MD5_MESSAGE_BYTES / 4; i++)
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secret[i] = net_secret[i];
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md5_transform(hash, secret);
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seq = hash[0] | (((u64)hash[1]) << 32);
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seq += ktime_to_ns(ktime_get_real());
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seq &= (1ull << 48) - 1;
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return seq;
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}
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EXPORT_SYMBOL(secure_dccpv6_sequence_number);
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#endif
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#endif
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