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tcp: TCP experimental option for SMC

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The SMC protocol [1] relies on the use of a new TCP experimental
option [2, 3]. With this option, SMC capabilities are exchanged
between peers during the TCP three way handshake. This patch adds
support for this experimental option to TCP.

References:
[1] SMC-R Informational RFC: http://www.rfc-editor.org/info/rfc7609
[2] Shared Use of TCP Experimental Options RFC 6994:
    https://tools.ietf.org/rfc/rfc6994.txt
[3] IANA ExID SMCR:
http://www.iana.org/assignments/tcp-parameters/tcp-parameters.xhtml#tcp-exids

Signed-off-by: Ursula Braun <ubraun@linux.vnet.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Ursula Braun 2017-10-25 11:01:45 +02:00 committed by David S. Miller
parent 145686baab
commit 60e2a77807
7 changed files with 136 additions and 6 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

9
include/linux/tcp.h
View file

@ -98,7 +98,8 @@ struct tcp_options_received {
tstamp_ok : 1, /* TIMESTAMP seen on SYN packet */
dsack : 1, /* D-SACK is scheduled */
wscale_ok : 1, /* Wscale seen on SYN packet */
sack_ok : 4, /* SACK seen on SYN packet */
sack_ok : 3, /* SACK seen on SYN packet */
smc_ok : 1, /* SMC seen on SYN packet */
snd_wscale : 4, /* Window scaling received from sender */
rcv_wscale : 4; /* Window scaling to send to receiver */
u8 num_sacks; /* Number of SACK blocks */
@ -110,6 +111,9 @@ static inline void tcp_clear_options(struct tcp_options_received *rx_opt)
{
rx_opt->tstamp_ok = rx_opt->sack_ok = 0;
rx_opt->wscale_ok = rx_opt->snd_wscale = 0;
#if IS_ENABLED(CONFIG_SMC)
rx_opt->smc_ok = 0;
#endif
}
/* This is the max number of SACKS that we'll generate and process. It's safe
@ -229,7 +233,8 @@ struct tcp_sock {
syn_fastopen_ch:1, /* Active TFO re-enabling probe */
syn_data_acked:1,/* data in SYN is acked by SYN-ACK */
save_syn:1, /* Save headers of SYN packet */
is_cwnd_limited:1;/* forward progress limited by snd_cwnd? */
is_cwnd_limited:1,/* forward progress limited by snd_cwnd? */
syn_smc:1; /* SYN includes SMC */
u32 tlp_high_seq; /* snd_nxt at the time of TLP retransmit. */
/* RTT measurement */

3
include/net/inet_sock.h
View file

@ -92,7 +92,8 @@ struct inet_request_sock {
wscale_ok : 1,
ecn_ok : 1,
acked : 1,
no_srccheck: 1;
no_srccheck: 1,
smc_ok : 1;
kmemcheck_bitfield_end(flags);
u32 ir_mark;
union {

7
include/net/tcp.h
View file

@ -191,6 +191,7 @@ void tcp_time_wait(struct sock *sk, int state, int timeo);
* experimental options. See draft-ietf-tcpm-experimental-options-00.txt
*/
#define TCPOPT_FASTOPEN_MAGIC 0xF989
#define TCPOPT_SMC_MAGIC 0xE2D4C3D9
/*
* TCP option lengths
@ -203,6 +204,7 @@ void tcp_time_wait(struct sock *sk, int state, int timeo);
#define TCPOLEN_MD5SIG 18
#define TCPOLEN_FASTOPEN_BASE 2
#define TCPOLEN_EXP_FASTOPEN_BASE 4
#define TCPOLEN_EXP_SMC_BASE 6
/* But this is what stacks really send out. */
#define TCPOLEN_TSTAMP_ALIGNED 12
@ -213,6 +215,7 @@ void tcp_time_wait(struct sock *sk, int state, int timeo);
#define TCPOLEN_SACK_PERBLOCK 8
#define TCPOLEN_MD5SIG_ALIGNED 20
#define TCPOLEN_MSS_ALIGNED 4
#define TCPOLEN_EXP_SMC_BASE_ALIGNED 8
/* Flags in tp->nonagle */
#define TCP_NAGLE_OFF 1 /* Nagle's algo is disabled */
@ -2108,4 +2111,8 @@ static inline bool tcp_bpf_ca_needs_ecn(struct sock *sk)
{
return (tcp_call_bpf(sk, BPF_SOCK_OPS_NEEDS_ECN) == 1);
}
#if IS_ENABLED(CONFIG_SMC)
extern struct static_key_false tcp_have_smc;
#endif
#endif /* _TCP_H */

6
net/ipv4/tcp.c
View file

@ -270,6 +270,7 @@
#include <linux/time.h>
#include <linux/slab.h>
#include <linux/errqueue.h>
#include <linux/static_key.h>
#include <net/icmp.h>
#include <net/inet_common.h>
@ -302,6 +303,11 @@ EXPORT_SYMBOL(sysctl_tcp_wmem);
atomic_long_t tcp_memory_allocated; /* Current allocated memory. */
EXPORT_SYMBOL(tcp_memory_allocated);
#if IS_ENABLED(CONFIG_SMC)
DEFINE_STATIC_KEY_FALSE(tcp_have_smc);
EXPORT_SYMBOL(tcp_have_smc);
#endif
/*
* Current number of TCP sockets.
*/

35
net/ipv4/tcp_input.c
View file

@ -76,6 +76,8 @@
#include <asm/unaligned.h>
#include <linux/errqueue.h>
#include <trace/events/tcp.h>
#include <linux/unaligned/access_ok.h>
#include <linux/static_key.h>
int sysctl_tcp_fack __read_mostly;
int sysctl_tcp_max_reordering __read_mostly = 300;
@ -3737,6 +3739,21 @@ static void tcp_parse_fastopen_option(int len, const unsigned char *cookie,
foc->exp = exp_opt;
}
static void smc_parse_options(const struct tcphdr *th,
struct tcp_options_received *opt_rx,
const unsigned char *ptr,
int opsize)
{
#if IS_ENABLED(CONFIG_SMC)
if (static_branch_unlikely(&tcp_have_smc)) {
if (th->syn && !(opsize & 1) &&
opsize >= TCPOLEN_EXP_SMC_BASE &&
get_unaligned_be32(ptr) == TCPOPT_SMC_MAGIC)
opt_rx->smc_ok = 1;
}
#endif
}
/* Look for tcp options. Normally only called on SYN and SYNACK packets.
* But, this can also be called on packets in the established flow when
* the fast version below fails.
@ -3844,6 +3861,9 @@ void tcp_parse_options(const struct net *net,
tcp_parse_fastopen_option(opsize -
TCPOLEN_EXP_FASTOPEN_BASE,
ptr + 2, th->syn, foc, true);
else
smc_parse_options(th, opt_rx, ptr,
opsize);
break;
}
@ -5598,6 +5618,16 @@ static bool tcp_rcv_fastopen_synack(struct sock *sk, struct sk_buff *synack,
return false;
}
static void smc_check_reset_syn(struct tcp_sock *tp)
{
#if IS_ENABLED(CONFIG_SMC)
if (static_branch_unlikely(&tcp_have_smc)) {
if (tp->syn_smc && !tp->rx_opt.smc_ok)
tp->syn_smc = 0;
}
#endif
}
static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb,
const struct tcphdr *th)
{
@ -5704,6 +5734,8 @@ static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb,
* is initialized. */
tp->copied_seq = tp->rcv_nxt;
smc_check_reset_syn(tp);
smp_mb();
tcp_finish_connect(sk, skb);
@ -6157,6 +6189,9 @@ static void tcp_openreq_init(struct request_sock *req,
ireq->ir_rmt_port = tcp_hdr(skb)->source;
ireq->ir_num = ntohs(tcp_hdr(skb)->dest);
ireq->ir_mark = inet_request_mark(sk, skb);
#if IS_ENABLED(CONFIG_SMC)
ireq->smc_ok = rx_opt->smc_ok;
#endif
}
struct request_sock *inet_reqsk_alloc(const struct request_sock_ops *ops,

19
net/ipv4/tcp_minisocks.c
View file

@ -23,6 +23,7 @@
#include <linux/slab.h>
#include <linux/sysctl.h>
#include <linux/workqueue.h>
#include <linux/static_key.h>
#include <net/tcp.h>
#include <net/inet_common.h>
#include <net/xfrm.h>
@ -416,6 +417,21 @@ void tcp_ca_openreq_child(struct sock *sk, const struct dst_entry *dst)
}
EXPORT_SYMBOL_GPL(tcp_ca_openreq_child);
static void smc_check_reset_syn_req(struct tcp_sock *oldtp,
struct request_sock *req,
struct tcp_sock *newtp)
{
#if IS_ENABLED(CONFIG_SMC)
struct inet_request_sock *ireq;
if (static_branch_unlikely(&tcp_have_smc)) {
ireq = inet_rsk(req);
if (oldtp->syn_smc && !ireq->smc_ok)
newtp->syn_smc = 0;
}
#endif
}
/* This is not only more efficient than what we used to do, it eliminates
* a lot of code duplication between IPv4/IPv6 SYN recv processing. -DaveM
*
@ -433,6 +449,9 @@ struct sock *tcp_create_openreq_child(const struct sock *sk,
struct tcp_request_sock *treq = tcp_rsk(req);
struct inet_connection_sock *newicsk = inet_csk(newsk);
struct tcp_sock *newtp = tcp_sk(newsk);
struct tcp_sock *oldtp = tcp_sk(sk);
smc_check_reset_syn_req(oldtp, req, newtp);
/* Now setup tcp_sock */
newtp->pred_flags = 0;

63
net/ipv4/tcp_output.c
View file

@ -41,6 +41,7 @@
#include <linux/compiler.h>
#include <linux/gfp.h>
#include <linux/module.h>
#include <linux/static_key.h>
#include <trace/events/tcp.h>
@ -422,6 +423,22 @@ static inline bool tcp_urg_mode(const struct tcp_sock *tp)
#define OPTION_MD5 (1 << 2)
#define OPTION_WSCALE (1 << 3)
#define OPTION_FAST_OPEN_COOKIE (1 << 8)
#define OPTION_SMC (1 << 9)
static void smc_options_write(__be32 *ptr, u16 *options)
{
#if IS_ENABLED(CONFIG_SMC)
if (static_branch_unlikely(&tcp_have_smc)) {
if (unlikely(OPTION_SMC & *options)) {
*ptr++ = htonl((TCPOPT_NOP << 24) |
(TCPOPT_NOP << 16) |
(TCPOPT_EXP << 8) |
(TCPOLEN_EXP_SMC_BASE));
*ptr++ = htonl(TCPOPT_SMC_MAGIC);
}
}
#endif
}
struct tcp_out_options {
u16 options; /* bit field of OPTION_* */
@ -540,6 +557,41 @@ static void tcp_options_write(__be32 *ptr, struct tcp_sock *tp,
}
ptr += (len + 3) >> 2;
}
smc_options_write(ptr, &options);
}
static void smc_set_option(const struct tcp_sock *tp,
struct tcp_out_options *opts,
unsigned int *remaining)
{
#if IS_ENABLED(CONFIG_SMC)
if (static_branch_unlikely(&tcp_have_smc)) {
if (tp->syn_smc) {
if (*remaining >= TCPOLEN_EXP_SMC_BASE_ALIGNED) {
opts->options |= OPTION_SMC;
*remaining -= TCPOLEN_EXP_SMC_BASE_ALIGNED;
}
}
}
#endif
}
static void smc_set_option_cond(const struct tcp_sock *tp,
const struct inet_request_sock *ireq,
struct tcp_out_options *opts,
unsigned int *remaining)
{
#if IS_ENABLED(CONFIG_SMC)
if (static_branch_unlikely(&tcp_have_smc)) {
if (tp->syn_smc && ireq->smc_ok) {
if (*remaining >= TCPOLEN_EXP_SMC_BASE_ALIGNED) {
opts->options |= OPTION_SMC;
*remaining -= TCPOLEN_EXP_SMC_BASE_ALIGNED;
}
}
}
#endif
}
/* Compute TCP options for SYN packets. This is not the final
@ -607,11 +659,14 @@ static unsigned int tcp_syn_options(struct sock *sk, struct sk_buff *skb,
}
}
smc_set_option(tp, opts, &remaining);
return MAX_TCP_OPTION_SPACE - remaining;
}
/* Set up TCP options for SYN-ACKs. */
static unsigned int tcp_synack_options(struct request_sock *req,
static unsigned int tcp_synack_options(const struct sock *sk,
struct request_sock *req,
unsigned int mss, struct sk_buff *skb,
struct tcp_out_options *opts,
const struct tcp_md5sig_key *md5,
@ -667,6 +722,8 @@ static unsigned int tcp_synack_options(struct request_sock *req,
}
}
smc_set_option_cond(tcp_sk(sk), ireq, opts, &remaining);
return MAX_TCP_OPTION_SPACE - remaining;
}
@ -3195,8 +3252,8 @@ struct sk_buff *tcp_make_synack(const struct sock *sk, struct dst_entry *dst,
md5 = tcp_rsk(req)->af_specific->req_md5_lookup(sk, req_to_sk(req));
#endif
skb_set_hash(skb, tcp_rsk(req)->txhash, PKT_HASH_TYPE_L4);
tcp_header_size = tcp_synack_options(req, mss, skb, &opts, md5, foc) +
sizeof(*th);
tcp_header_size = tcp_synack_options(sk, req, mss, skb, &opts, md5,
foc) + sizeof(*th);
skb_push(skb, tcp_header_size);
skb_reset_transport_header(skb);