tcp: TCP experimental option for SMC
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
David S. Miller
parent
145686baab
commit
60e2a77807
@ -98,7 +98,8 @@ struct tcp_options_received {
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tstamp_ok : 1, /* TIMESTAMP seen on SYN packet */
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dsack : 1, /* D-SACK is scheduled */
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wscale_ok : 1, /* Wscale seen on SYN packet */
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sack_ok : 4, /* SACK seen on SYN packet */
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sack_ok : 3, /* SACK seen on SYN packet */
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smc_ok : 1, /* SMC seen on SYN packet */
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snd_wscale : 4, /* Window scaling received from sender */
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rcv_wscale : 4; /* Window scaling to send to receiver */
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u8 num_sacks; /* Number of SACK blocks */
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@ -110,6 +111,9 @@ static inline void tcp_clear_options(struct tcp_options_received *rx_opt)
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{
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rx_opt->tstamp_ok = rx_opt->sack_ok = 0;
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rx_opt->wscale_ok = rx_opt->snd_wscale = 0;
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#if IS_ENABLED(CONFIG_SMC)
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rx_opt->smc_ok = 0;
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#endif
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}
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/* This is the max number of SACKS that we'll generate and process. It's safe
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@ -229,7 +233,8 @@ struct tcp_sock {
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syn_fastopen_ch:1, /* Active TFO re-enabling probe */
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syn_data_acked:1,/* data in SYN is acked by SYN-ACK */
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save_syn:1, /* Save headers of SYN packet */
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is_cwnd_limited:1;/* forward progress limited by snd_cwnd? */
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is_cwnd_limited:1,/* forward progress limited by snd_cwnd? */
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syn_smc:1; /* SYN includes SMC */
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u32 tlp_high_seq; /* snd_nxt at the time of TLP retransmit. */
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/* RTT measurement */
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@ -92,7 +92,8 @@ struct inet_request_sock {
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wscale_ok : 1,
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ecn_ok : 1,
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acked : 1,
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no_srccheck: 1;
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no_srccheck: 1,
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smc_ok : 1;
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kmemcheck_bitfield_end(flags);
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u32 ir_mark;
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union {
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@ -191,6 +191,7 @@ void tcp_time_wait(struct sock *sk, int state, int timeo);
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* experimental options. See draft-ietf-tcpm-experimental-options-00.txt
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*/
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#define TCPOPT_FASTOPEN_MAGIC 0xF989
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#define TCPOPT_SMC_MAGIC 0xE2D4C3D9
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/*
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* TCP option lengths
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@ -203,6 +204,7 @@ void tcp_time_wait(struct sock *sk, int state, int timeo);
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#define TCPOLEN_MD5SIG 18
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#define TCPOLEN_FASTOPEN_BASE 2
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#define TCPOLEN_EXP_FASTOPEN_BASE 4
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#define TCPOLEN_EXP_SMC_BASE 6
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/* But this is what stacks really send out. */
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#define TCPOLEN_TSTAMP_ALIGNED 12
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@ -213,6 +215,7 @@ void tcp_time_wait(struct sock *sk, int state, int timeo);
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#define TCPOLEN_SACK_PERBLOCK 8
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#define TCPOLEN_MD5SIG_ALIGNED 20
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#define TCPOLEN_MSS_ALIGNED 4
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#define TCPOLEN_EXP_SMC_BASE_ALIGNED 8
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/* Flags in tp->nonagle */
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#define TCP_NAGLE_OFF 1 /* Nagle's algo is disabled */
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@ -2108,4 +2111,8 @@ static inline bool tcp_bpf_ca_needs_ecn(struct sock *sk)
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{
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return (tcp_call_bpf(sk, BPF_SOCK_OPS_NEEDS_ECN) == 1);
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}
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#if IS_ENABLED(CONFIG_SMC)
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extern struct static_key_false tcp_have_smc;
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#endif
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#endif /* _TCP_H */
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@ -270,6 +270,7 @@
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#include <linux/time.h>
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#include <linux/slab.h>
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#include <linux/errqueue.h>
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#include <linux/static_key.h>
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#include <net/icmp.h>
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#include <net/inet_common.h>
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@ -302,6 +303,11 @@ EXPORT_SYMBOL(sysctl_tcp_wmem);
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atomic_long_t tcp_memory_allocated; /* Current allocated memory. */
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EXPORT_SYMBOL(tcp_memory_allocated);
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#if IS_ENABLED(CONFIG_SMC)
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DEFINE_STATIC_KEY_FALSE(tcp_have_smc);
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EXPORT_SYMBOL(tcp_have_smc);
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#endif
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/*
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* Current number of TCP sockets.
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*/
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@ -76,6 +76,8 @@
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#include <asm/unaligned.h>
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#include <linux/errqueue.h>
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#include <trace/events/tcp.h>
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#include <linux/unaligned/access_ok.h>
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#include <linux/static_key.h>
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int sysctl_tcp_fack __read_mostly;
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int sysctl_tcp_max_reordering __read_mostly = 300;
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@ -3737,6 +3739,21 @@ static void tcp_parse_fastopen_option(int len, const unsigned char *cookie,
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foc->exp = exp_opt;
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}
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static void smc_parse_options(const struct tcphdr *th,
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struct tcp_options_received *opt_rx,
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const unsigned char *ptr,
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int opsize)
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{
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#if IS_ENABLED(CONFIG_SMC)
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if (static_branch_unlikely(&tcp_have_smc)) {
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if (th->syn && !(opsize & 1) &&
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opsize >= TCPOLEN_EXP_SMC_BASE &&
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get_unaligned_be32(ptr) == TCPOPT_SMC_MAGIC)
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opt_rx->smc_ok = 1;
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}
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#endif
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}
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/* Look for tcp options. Normally only called on SYN and SYNACK packets.
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* But, this can also be called on packets in the established flow when
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* the fast version below fails.
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@ -3844,6 +3861,9 @@ void tcp_parse_options(const struct net *net,
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tcp_parse_fastopen_option(opsize -
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TCPOLEN_EXP_FASTOPEN_BASE,
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ptr + 2, th->syn, foc, true);
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else
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smc_parse_options(th, opt_rx, ptr,
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opsize);
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break;
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}
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@ -5598,6 +5618,16 @@ static bool tcp_rcv_fastopen_synack(struct sock *sk, struct sk_buff *synack,
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return false;
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}
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static void smc_check_reset_syn(struct tcp_sock *tp)
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{
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#if IS_ENABLED(CONFIG_SMC)
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if (static_branch_unlikely(&tcp_have_smc)) {
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if (tp->syn_smc && !tp->rx_opt.smc_ok)
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tp->syn_smc = 0;
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}
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#endif
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}
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static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb,
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const struct tcphdr *th)
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{
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@ -5704,6 +5734,8 @@ static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb,
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* is initialized. */
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tp->copied_seq = tp->rcv_nxt;
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smc_check_reset_syn(tp);
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smp_mb();
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tcp_finish_connect(sk, skb);
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@ -6157,6 +6189,9 @@ static void tcp_openreq_init(struct request_sock *req,
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ireq->ir_rmt_port = tcp_hdr(skb)->source;
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ireq->ir_num = ntohs(tcp_hdr(skb)->dest);
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ireq->ir_mark = inet_request_mark(sk, skb);
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#if IS_ENABLED(CONFIG_SMC)
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ireq->smc_ok = rx_opt->smc_ok;
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#endif
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}
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struct request_sock *inet_reqsk_alloc(const struct request_sock_ops *ops,
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@ -23,6 +23,7 @@
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#include <linux/slab.h>
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#include <linux/sysctl.h>
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#include <linux/workqueue.h>
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#include <linux/static_key.h>
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#include <net/tcp.h>
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#include <net/inet_common.h>
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#include <net/xfrm.h>
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@ -416,6 +417,21 @@ void tcp_ca_openreq_child(struct sock *sk, const struct dst_entry *dst)
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}
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EXPORT_SYMBOL_GPL(tcp_ca_openreq_child);
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static void smc_check_reset_syn_req(struct tcp_sock *oldtp,
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struct request_sock *req,
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struct tcp_sock *newtp)
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{
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#if IS_ENABLED(CONFIG_SMC)
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struct inet_request_sock *ireq;
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if (static_branch_unlikely(&tcp_have_smc)) {
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ireq = inet_rsk(req);
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if (oldtp->syn_smc && !ireq->smc_ok)
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newtp->syn_smc = 0;
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}
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#endif
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}
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/* This is not only more efficient than what we used to do, it eliminates
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* a lot of code duplication between IPv4/IPv6 SYN recv processing. -DaveM
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*
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@ -433,6 +449,9 @@ struct sock *tcp_create_openreq_child(const struct sock *sk,
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struct tcp_request_sock *treq = tcp_rsk(req);
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struct inet_connection_sock *newicsk = inet_csk(newsk);
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struct tcp_sock *newtp = tcp_sk(newsk);
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struct tcp_sock *oldtp = tcp_sk(sk);
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smc_check_reset_syn_req(oldtp, req, newtp);
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/* Now setup tcp_sock */
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newtp->pred_flags = 0;
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@ -41,6 +41,7 @@
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#include <linux/compiler.h>
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#include <linux/gfp.h>
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#include <linux/module.h>
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#include <linux/static_key.h>
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#include <trace/events/tcp.h>
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@ -422,6 +423,22 @@ static inline bool tcp_urg_mode(const struct tcp_sock *tp)
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#define OPTION_MD5 (1 << 2)
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#define OPTION_WSCALE (1 << 3)
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#define OPTION_FAST_OPEN_COOKIE (1 << 8)
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#define OPTION_SMC (1 << 9)
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static void smc_options_write(__be32 *ptr, u16 *options)
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{
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#if IS_ENABLED(CONFIG_SMC)
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if (static_branch_unlikely(&tcp_have_smc)) {
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if (unlikely(OPTION_SMC & *options)) {
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*ptr++ = htonl((TCPOPT_NOP << 24) |
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(TCPOPT_NOP << 16) |
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(TCPOPT_EXP << 8) |
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(TCPOLEN_EXP_SMC_BASE));
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*ptr++ = htonl(TCPOPT_SMC_MAGIC);
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}
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}
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#endif
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}
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struct tcp_out_options {
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u16 options; /* bit field of OPTION_* */
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@ -540,6 +557,41 @@ static void tcp_options_write(__be32 *ptr, struct tcp_sock *tp,
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}
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ptr += (len + 3) >> 2;
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}
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smc_options_write(ptr, &options);
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}
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static void smc_set_option(const struct tcp_sock *tp,
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struct tcp_out_options *opts,
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unsigned int *remaining)
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{
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#if IS_ENABLED(CONFIG_SMC)
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if (static_branch_unlikely(&tcp_have_smc)) {
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if (tp->syn_smc) {
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if (*remaining >= TCPOLEN_EXP_SMC_BASE_ALIGNED) {
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opts->options |= OPTION_SMC;
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*remaining -= TCPOLEN_EXP_SMC_BASE_ALIGNED;
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}
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}
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}
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#endif
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}
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static void smc_set_option_cond(const struct tcp_sock *tp,
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const struct inet_request_sock *ireq,
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struct tcp_out_options *opts,
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unsigned int *remaining)
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{
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#if IS_ENABLED(CONFIG_SMC)
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if (static_branch_unlikely(&tcp_have_smc)) {
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if (tp->syn_smc && ireq->smc_ok) {
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if (*remaining >= TCPOLEN_EXP_SMC_BASE_ALIGNED) {
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opts->options |= OPTION_SMC;
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*remaining -= TCPOLEN_EXP_SMC_BASE_ALIGNED;
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}
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}
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}
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#endif
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}
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/* Compute TCP options for SYN packets. This is not the final
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@ -607,11 +659,14 @@ static unsigned int tcp_syn_options(struct sock *sk, struct sk_buff *skb,
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}
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}
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smc_set_option(tp, opts, &remaining);
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return MAX_TCP_OPTION_SPACE - remaining;
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}
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/* Set up TCP options for SYN-ACKs. */
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static unsigned int tcp_synack_options(struct request_sock *req,
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static unsigned int tcp_synack_options(const struct sock *sk,
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struct request_sock *req,
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unsigned int mss, struct sk_buff *skb,
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struct tcp_out_options *opts,
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const struct tcp_md5sig_key *md5,
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@ -667,6 +722,8 @@ static unsigned int tcp_synack_options(struct request_sock *req,
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}
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}
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smc_set_option_cond(tcp_sk(sk), ireq, opts, &remaining);
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return MAX_TCP_OPTION_SPACE - remaining;
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}
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@ -3195,8 +3252,8 @@ struct sk_buff *tcp_make_synack(const struct sock *sk, struct dst_entry *dst,
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md5 = tcp_rsk(req)->af_specific->req_md5_lookup(sk, req_to_sk(req));
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#endif
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skb_set_hash(skb, tcp_rsk(req)->txhash, PKT_HASH_TYPE_L4);
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tcp_header_size = tcp_synack_options(req, mss, skb, &opts, md5, foc) +
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sizeof(*th);
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tcp_header_size = tcp_synack_options(sk, req, mss, skb, &opts, md5,
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foc) + sizeof(*th);
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skb_push(skb, tcp_header_size);
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skb_reset_transport_header(skb);
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