tcp: options clean up (33ad798c) · Commits · 戴 / test

include/net/tcp.h

+2 −0

Original line number	Diff line number	Diff line
		@@ -50,6 +50,7 @@ extern atomic_t tcp_orphan_count;
		extern void tcp_time_wait(struct sock *sk, int state, int timeo);

		#define MAX_TCP_HEADER (128 + MAX_HEADER)
		#define MAX_TCP_OPTION_SPACE 40

		/*
		* Never offer a window over 32767 without using window scaling. Some
		@@ -184,6 +185,7 @@ extern void tcp_time_wait(struct sock *sk, int state, int timeo);
		#define TCPOLEN_SACK_BASE_ALIGNED 4
		#define TCPOLEN_SACK_PERBLOCK 8
		#define TCPOLEN_MD5SIG_ALIGNED 20
		#define TCPOLEN_MSS_ALIGNED 4

		/* Flags in tp->nonagle */
		#define TCP_NAGLE_OFF 1 /* Nagle's algo is disabled */

net/ipv4/tcp_output.c

+236 −196

Original line number	Diff line number	Diff line
		@@ -345,28 +345,82 @@ static void tcp_init_nondata_skb(struct sk_buff *skb, u32 seq, u8 flags)
		TCP_SKB_CB(skb)->end_seq = seq;
		}

		static void tcp_build_and_update_options(__be32 ptr, struct tcp_sock tp,
		__u32 tstamp, __u8 **md5_hash)
		{
		if (tp->rx_opt.tstamp_ok) {
		#define OPTION_SACK_ADVERTISE (1 << 0)
		#define OPTION_TS (1 << 1)
		#define OPTION_MD5 (1 << 2)

		struct tcp_out_options {
		u8 options; /* bit field of OPTION_* */
		u8 ws; /* window scale, 0 to disable */
		u8 num_sack_blocks; /* number of SACK blocks to include */
		u16 mss; /* 0 to disable */
		__u32 tsval, tsecr; /* need to include OPTION_TS */
		};

		static void tcp_options_write(__be32 ptr, struct tcp_sock tp,
		const struct tcp_out_options *opts,
		__u8 **md5_hash) {
		if (unlikely(OPTION_MD5 & opts->options)) {
		*ptr++ = htonl((TCPOPT_NOP << 24) \|
		(TCPOPT_NOP << 16) \|
		(TCPOPT_MD5SIG << 8) \|
		TCPOLEN_MD5SIG);
		md5_hash = (__u8 )ptr;
		ptr += 4;
		} else {
		*md5_hash = NULL;
		}

		if (likely(OPTION_TS & opts->options)) {
		if (unlikely(OPTION_SACK_ADVERTISE & opts->options)) {
		*ptr++ = htonl((TCPOPT_SACK_PERM << 24) \|
		(TCPOLEN_SACK_PERM << 16) \|
		(TCPOPT_TIMESTAMP << 8) \|
		TCPOLEN_TIMESTAMP);
		} else {
		*ptr++ = htonl((TCPOPT_NOP << 24) \|
		(TCPOPT_NOP << 16) \|
		(TCPOPT_TIMESTAMP << 8) \|
		TCPOLEN_TIMESTAMP);
		*ptr++ = htonl(tstamp);
		*ptr++ = htonl(tp->rx_opt.ts_recent);
		}
		if (tp->rx_opt.eff_sacks) {
		struct tcp_sack_block *sp = tp->rx_opt.dsack ? tp->duplicate_sack : tp->selective_acks;
		*ptr++ = htonl(opts->tsval);
		*ptr++ = htonl(opts->tsecr);
		}

		if (unlikely(opts->mss)) {
		*ptr++ = htonl((TCPOPT_MSS << 24) \|
		(TCPOLEN_MSS << 16) \|
		opts->mss);
		}

		if (unlikely(OPTION_SACK_ADVERTISE & opts->options &&
		!(OPTION_TS & opts->options))) {
		*ptr++ = htonl((TCPOPT_NOP << 24) \|
		(TCPOPT_NOP << 16) \|
		(TCPOPT_SACK_PERM << 8) \|
		TCPOLEN_SACK_PERM);
		}

		if (unlikely(opts->ws)) {
		*ptr++ = htonl((TCPOPT_NOP << 24) \|
		(TCPOPT_WINDOW << 16) \|
		(TCPOLEN_WINDOW << 8) \|
		opts->ws);
		}

		if (unlikely(opts->num_sack_blocks)) {
		struct tcp_sack_block *sp = tp->rx_opt.dsack ?
		tp->duplicate_sack : tp->selective_acks;
		int this_sack;

		*ptr++ = htonl((TCPOPT_NOP << 24) \|
		(TCPOPT_NOP << 16) \|
		(TCPOPT_SACK << 8) \|
		(TCPOLEN_SACK_BASE + (tp->rx_opt.eff_sacks *
		(TCPOLEN_SACK_BASE + (opts->num_sack_blocks *
		TCPOLEN_SACK_PERBLOCK)));

		for (this_sack = 0; this_sack < tp->rx_opt.eff_sacks; this_sack++) {
		for (this_sack = 0; this_sack < opts->num_sack_blocks;
		++this_sack) {
		*ptr++ = htonl(sp[this_sack].start_seq);
		*ptr++ = htonl(sp[this_sack].end_seq);
		}
		@@ -376,81 +430,137 @@ static void tcp_build_and_update_options(__be32 ptr, struct tcp_sock tp,
		tp->rx_opt.eff_sacks--;
		}
		}
		}

		static unsigned tcp_syn_options(struct sock sk, struct sk_buff skb,
		struct tcp_out_options *opts,
		struct tcp_md5sig_key **md5) {
		struct tcp_sock *tp = tcp_sk(sk);
		unsigned size = 0;

		#ifdef CONFIG_TCP_MD5SIG
		if (md5_hash) {
		*ptr++ = htonl((TCPOPT_NOP << 24) \|
		(TCPOPT_NOP << 16) \|
		(TCPOPT_MD5SIG << 8) \|
		TCPOLEN_MD5SIG);
		md5_hash = (__u8 )ptr;
		*md5 = tp->af_specific->md5_lookup(sk, sk);
		if (*md5) {
		opts->options \|= OPTION_MD5;
		size += TCPOLEN_MD5SIG_ALIGNED;
		}
		#else
		*md5 = NULL;
		#endif

		/* We always get an MSS option. The option bytes which will be seen in
		* normal data packets should timestamps be used, must be in the MSS
		* advertised. But we subtract them from tp->mss_cache so that
		* calculations in tcp_sendmsg are simpler etc. So account for this
		* fact here if necessary. If we don't do this correctly, as a
		* receiver we won't recognize data packets as being full sized when we
		* should, and thus we won't abide by the delayed ACK rules correctly.
		* SACKs don't matter, we never delay an ACK when we have any of those
		* going out. */
		opts->mss = tcp_advertise_mss(sk);
		size += TCPOLEN_MSS_ALIGNED;

		if (likely(sysctl_tcp_timestamps && *md5 == NULL)) {
		opts->options \|= OPTION_TS;
		opts->tsval = TCP_SKB_CB(skb)->when;
		opts->tsecr = tp->rx_opt.ts_recent;
		size += TCPOLEN_TSTAMP_ALIGNED;
		}
		if (likely(sysctl_tcp_window_scaling)) {
		opts->ws = tp->rx_opt.rcv_wscale;
		size += TCPOLEN_WSCALE_ALIGNED;
		}
		if (likely(sysctl_tcp_sack)) {
		opts->options \|= OPTION_SACK_ADVERTISE;
		if (unlikely(!OPTION_TS & opts->options))
		size += TCPOLEN_SACKPERM_ALIGNED;
		}

		return size;
		}

		static unsigned tcp_synack_options(struct sock *sk,
		struct request_sock *req,
		unsigned mss, struct sk_buff *skb,
		struct tcp_out_options *opts,
		struct tcp_md5sig_key **md5) {
		unsigned size = 0;
		struct inet_request_sock *ireq = inet_rsk(req);
		char doing_ts;

		#ifdef CONFIG_TCP_MD5SIG
		*md5 = tcp_rsk(req)->af_specific->md5_lookup(sk, req);
		if (*md5) {
		opts->options \|= OPTION_MD5;
		size += TCPOLEN_MD5SIG_ALIGNED;
		}
		#else
		*md5 = NULL;
		#endif

		/* we can't fit any SACK blocks in a packet with MD5 + TS
		options. There was discussion about disabling SACK rather than TS in
		order to fit in better with old, buggy kernels, but that was deemed
		to be unnecessary. */
		doing_ts = ireq->tstamp_ok && !(*md5 && ireq->sack_ok);

		opts->mss = mss;
		size += TCPOLEN_MSS_ALIGNED;

		if (likely(ireq->wscale_ok)) {
		opts->ws = ireq->rcv_wscale;
		size += TCPOLEN_WSCALE_ALIGNED;
		}
		if (likely(doing_ts)) {
		opts->options \|= OPTION_TS;
		opts->tsval = TCP_SKB_CB(skb)->when;
		opts->tsecr = req->ts_recent;
		size += TCPOLEN_TSTAMP_ALIGNED;
		}
		if (likely(ireq->sack_ok)) {
		opts->options \|= OPTION_SACK_ADVERTISE;
		if (unlikely(!doing_ts))
		size += TCPOLEN_SACKPERM_ALIGNED;
		}

		return size;
		}

		static unsigned tcp_established_options(struct sock sk, struct sk_buff skb,
		struct tcp_out_options *opts,
		struct tcp_md5sig_key **md5) {
		struct tcp_skb_cb *tcb = skb ? TCP_SKB_CB(skb) : NULL;
		struct tcp_sock *tp = tcp_sk(sk);
		unsigned size = 0;

		/* Construct a tcp options header for a SYN or SYN_ACK packet.
		* If this is every changed make sure to change the definition of
		* MAX_SYN_SIZE to match the new maximum number of options that you
		* can generate.
		*
		* Note - that with the RFC2385 TCP option, we make room for the
		* 16 byte MD5 hash. This will be filled in later, so the pointer for the
		* location to be filled is passed back up.
		*/
		static void tcp_syn_build_options(__be32 *ptr, int mss, int ts, int sack,
		int offer_wscale, int wscale, __u32 tstamp,
		__u32 ts_recent, __u8 **md5_hash)
		{
		/* We always get an MSS option.
		* The option bytes which will be seen in normal data
		* packets should timestamps be used, must be in the MSS
		* advertised. But we subtract them from tp->mss_cache so
		* that calculations in tcp_sendmsg are simpler etc.
		* So account for this fact here if necessary. If we
		* don't do this correctly, as a receiver we won't
		* recognize data packets as being full sized when we
		* should, and thus we won't abide by the delayed ACK
		* rules correctly.
		* SACKs don't matter, we never delay an ACK when we
		* have any of those going out.
		*/
		*ptr++ = htonl((TCPOPT_MSS << 24) \| (TCPOLEN_MSS << 16) \| mss);
		if (ts) {
		if (sack)
		*ptr++ = htonl((TCPOPT_SACK_PERM << 24) \|
		(TCPOLEN_SACK_PERM << 16) \|
		(TCPOPT_TIMESTAMP << 8) \|
		TCPOLEN_TIMESTAMP);
		else
		*ptr++ = htonl((TCPOPT_NOP << 24) \|
		(TCPOPT_NOP << 16) \|
		(TCPOPT_TIMESTAMP << 8) \|
		TCPOLEN_TIMESTAMP);
		ptr++ = htonl(tstamp); / TSVAL */
		ptr++ = htonl(ts_recent); / TSECR */
		} else if (sack)
		*ptr++ = htonl((TCPOPT_NOP << 24) \|
		(TCPOPT_NOP << 16) \|
		(TCPOPT_SACK_PERM << 8) \|
		TCPOLEN_SACK_PERM);
		if (offer_wscale)
		*ptr++ = htonl((TCPOPT_NOP << 24) \|
		(TCPOPT_WINDOW << 16) \|
		(TCPOLEN_WINDOW << 8) \|
		(wscale));
		#ifdef CONFIG_TCP_MD5SIG
		/*
		* If MD5 is enabled, then we set the option, and include the size
		* (always 18). The actual MD5 hash is added just before the
		* packet is sent.
		*/
		if (md5_hash) {
		*ptr++ = htonl((TCPOPT_NOP << 24) \|
		(TCPOPT_NOP << 16) \|
		(TCPOPT_MD5SIG << 8) \|
		TCPOLEN_MD5SIG);
		md5_hash = (__u8 )ptr;
		*md5 = tp->af_specific->md5_lookup(sk, sk);
		if (unlikely(*md5)) {
		opts->options \|= OPTION_MD5;
		size += TCPOLEN_MD5SIG_ALIGNED;
		}
		#else
		*md5 = NULL;
		#endif

		if (likely(tp->rx_opt.tstamp_ok)) {
		opts->options \|= OPTION_TS;
		opts->tsval = tcb ? tcb->when : 0;
		opts->tsecr = tp->rx_opt.ts_recent;
		size += TCPOLEN_TSTAMP_ALIGNED;
		}

		if (unlikely(tp->rx_opt.eff_sacks)) {
		const unsigned remaining = MAX_TCP_OPTION_SPACE - size;
		opts->num_sack_blocks =
		min_t(unsigned, tp->rx_opt.eff_sacks,
		(remaining - TCPOLEN_SACK_BASE_ALIGNED) /
		TCPOLEN_SACK_PERBLOCK);
		size += TCPOLEN_SACK_BASE_ALIGNED +
		opts->num_sack_blocks * TCPOLEN_SACK_PERBLOCK;
		}

		return size;
		}

		/* This routine actually transmits TCP packets queued in by
		@@ -471,13 +581,11 @@ static int tcp_transmit_skb(struct sock sk, struct sk_buff skb, int clone_it,
		struct inet_sock *inet;
		struct tcp_sock *tp;
		struct tcp_skb_cb *tcb;
		int tcp_header_size;
		#ifdef CONFIG_TCP_MD5SIG
		struct tcp_out_options opts;
		unsigned tcp_options_size, tcp_header_size;
		struct tcp_md5sig_key *md5;
		__u8 *md5_hash_location;
		#endif
		struct tcphdr *th;
		int sysctl_flags;
		int err;

		BUG_ON(!skb \|\| !tcp_skb_pcount(skb));
		@@ -500,52 +608,18 @@ static int tcp_transmit_skb(struct sock sk, struct sk_buff skb, int clone_it,
		inet = inet_sk(sk);
		tp = tcp_sk(sk);
		tcb = TCP_SKB_CB(skb);
		tcp_header_size = tp->tcp_header_len;
		memset(&opts, 0, sizeof(opts));

		#define SYSCTL_FLAG_TSTAMPS 0x1
		#define SYSCTL_FLAG_WSCALE 0x2
		#define SYSCTL_FLAG_SACK 0x4

		sysctl_flags = 0;
		if (unlikely(tcb->flags & TCPCB_FLAG_SYN)) {
		tcp_header_size = sizeof(struct tcphdr) + TCPOLEN_MSS;
		if (sysctl_tcp_timestamps) {
		tcp_header_size += TCPOLEN_TSTAMP_ALIGNED;
		sysctl_flags \|= SYSCTL_FLAG_TSTAMPS;
		}
		if (sysctl_tcp_window_scaling) {
		tcp_header_size += TCPOLEN_WSCALE_ALIGNED;
		sysctl_flags \|= SYSCTL_FLAG_WSCALE;
		}
		if (sysctl_tcp_sack) {
		sysctl_flags \|= SYSCTL_FLAG_SACK;
		if (!(sysctl_flags & SYSCTL_FLAG_TSTAMPS))
		tcp_header_size += TCPOLEN_SACKPERM_ALIGNED;
		}
		} else if (unlikely(tp->rx_opt.eff_sacks)) {
		/* A SACK is 2 pad bytes, a 2 byte header, plus
		* 2 32-bit sequence numbers for each SACK block.
		*/
		tcp_header_size += (TCPOLEN_SACK_BASE_ALIGNED +
		(tp->rx_opt.eff_sacks *
		TCPOLEN_SACK_PERBLOCK));
		}
		if (unlikely(tcb->flags & TCPCB_FLAG_SYN))
		tcp_options_size = tcp_syn_options(sk, skb, &opts, &md5);
		else
		tcp_options_size = tcp_established_options(sk, skb, &opts,
		&md5);
		tcp_header_size = tcp_options_size + sizeof(struct tcphdr);

		if (tcp_packets_in_flight(tp) == 0)
		tcp_ca_event(sk, CA_EVENT_TX_START);

		#ifdef CONFIG_TCP_MD5SIG
		/*
		* Are we doing MD5 on this segment? If so - make
		* room for it.
		*/
		md5 = tp->af_specific->md5_lookup(sk, sk);
		if (md5) {
		tcp_header_size += TCPOLEN_MD5SIG_ALIGNED;
		sk->sk_route_caps &= ~NETIF_F_GSO_MASK;
		}
		#endif

		skb_push(skb, tcp_header_size);
		skb_reset_transport_header(skb);
		skb_set_owner_w(skb, sk);
		@@ -576,33 +650,14 @@ static int tcp_transmit_skb(struct sock sk, struct sk_buff skb, int clone_it,
		th->urg = 1;
		}

		if (unlikely(tcb->flags & TCPCB_FLAG_SYN)) {
		tcp_syn_build_options((__be32 *)(th + 1),
		tcp_advertise_mss(sk),
		(sysctl_flags & SYSCTL_FLAG_TSTAMPS),
		(sysctl_flags & SYSCTL_FLAG_SACK),
		(sysctl_flags & SYSCTL_FLAG_WSCALE),
		tp->rx_opt.rcv_wscale,
		tcb->when,
		tp->rx_opt.ts_recent,

		#ifdef CONFIG_TCP_MD5SIG
		md5 ? &md5_hash_location :
		#endif
		NULL);
		} else {
		tcp_build_and_update_options((__be32 *)(th + 1),
		tp, tcb->when,
		#ifdef CONFIG_TCP_MD5SIG
		md5 ? &md5_hash_location :
		#endif
		NULL);
		tcp_options_write((__be32 *)(th + 1), tp, &opts, &md5_hash_location);
		if (likely((tcb->flags & TCPCB_FLAG_SYN) == 0))
		TCP_ECN_send(sk, skb, tcp_header_size);
		}

		#ifdef CONFIG_TCP_MD5SIG
		/* Calculate the MD5 hash, as we have all we need now */
		if (md5) {
		sk->sk_route_caps &= ~NETIF_F_GSO_MASK;
		tp->af_specific->calc_md5_hash(md5_hash_location,
		md5, sk, NULL, skb);
		}
		@@ -626,10 +681,6 @@ static int tcp_transmit_skb(struct sock sk, struct sk_buff skb, int clone_it,
		tcp_enter_cwr(sk, 1);

		return net_xmit_eval(err);

		#undef SYSCTL_FLAG_TSTAMPS
		#undef SYSCTL_FLAG_WSCALE
		#undef SYSCTL_FLAG_SACK
		}

		/* This routine just queue's the buffer
		@@ -970,6 +1021,9 @@ unsigned int tcp_current_mss(struct sock *sk, int large_allowed)
		u32 mss_now;
		u16 xmit_size_goal;
		int doing_tso = 0;
		unsigned header_len;
		struct tcp_out_options opts;
		struct tcp_md5sig_key *md5;

		mss_now = tp->mss_cache;

		@@ -982,14 +1036,16 @@ unsigned int tcp_current_mss(struct sock *sk, int large_allowed)
		mss_now = tcp_sync_mss(sk, mtu);
		}

		if (tp->rx_opt.eff_sacks)
		mss_now -= (TCPOLEN_SACK_BASE_ALIGNED +
		(tp->rx_opt.eff_sacks * TCPOLEN_SACK_PERBLOCK));

		#ifdef CONFIG_TCP_MD5SIG
		if (tp->af_specific->md5_lookup(sk, sk))
		mss_now -= TCPOLEN_MD5SIG_ALIGNED;
		#endif
		header_len = tcp_established_options(sk, NULL, &opts, &md5) +
		sizeof(struct tcphdr);
		/* The mss_cache is sized based on tp->tcp_header_len, which assumes
		* some common options. If this is an odd packet (because we have SACK
		* blocks etc) then our calculated header_len will be different, and
		* we have to adjust mss_now correspondingly */
		if (header_len != tp->tcp_header_len) {
		int delta = (int) header_len - tp->tcp_header_len;
		mss_now -= delta;
		}

		xmit_size_goal = mss_now;

		@@ -2179,11 +2235,10 @@ struct sk_buff tcp_make_synack(struct sock sk, struct dst_entry *dst,
		struct tcp_sock *tp = tcp_sk(sk);
		struct tcphdr *th;
		int tcp_header_size;
		struct tcp_out_options opts;
		struct sk_buff *skb;
		#ifdef CONFIG_TCP_MD5SIG
		struct tcp_md5sig_key *md5;
		__u8 *md5_hash_location;
		#endif

		skb = sock_wmalloc(sk, MAX_TCP_HEADER + 15, 1, GFP_ATOMIC);
		if (skb == NULL)
		@@ -2194,18 +2249,27 @@ struct sk_buff tcp_make_synack(struct sock sk, struct dst_entry *dst,

		skb->dst = dst_clone(dst);

		tcp_header_size = (sizeof(struct tcphdr) + TCPOLEN_MSS +
		(ireq->tstamp_ok ? TCPOLEN_TSTAMP_ALIGNED : 0) +
		(ireq->wscale_ok ? TCPOLEN_WSCALE_ALIGNED : 0) +
		/* SACK_PERM is in the place of NOP NOP of TS */
		((ireq->sack_ok && !ireq->tstamp_ok) ? TCPOLEN_SACKPERM_ALIGNED : 0));
		if (req->rcv_wnd == 0) { /* ignored for retransmitted syns */
		__u8 rcv_wscale;
		/* Set this up on the first call only */
		req->window_clamp = tp->window_clamp ? : dst_metric(dst, RTAX_WINDOW);
		/* tcp_full_space because it is guaranteed to be the first packet */
		tcp_select_initial_window(tcp_full_space(sk),
		dst_metric(dst, RTAX_ADVMSS) - (ireq->tstamp_ok ? TCPOLEN_TSTAMP_ALIGNED : 0),
		&req->rcv_wnd,
		&req->window_clamp,
		ireq->wscale_ok,
		&rcv_wscale);
		ireq->rcv_wscale = rcv_wscale;
		}

		memset(&opts, 0, sizeof(opts));
		TCP_SKB_CB(skb)->when = tcp_time_stamp;
		tcp_header_size = tcp_synack_options(sk, req,
		dst_metric(dst, RTAX_ADVMSS),
		skb, &opts, &md5) +
		sizeof(struct tcphdr);

		#ifdef CONFIG_TCP_MD5SIG
		/* Are we doing MD5 on this segment? If so - make room for it */
		md5 = tcp_rsk(req)->af_specific->md5_lookup(sk, req);
		if (md5)
		tcp_header_size += TCPOLEN_MD5SIG_ALIGNED;
		#endif
		skb_push(skb, tcp_header_size);
		skb_reset_transport_header(skb);

		@@ -2223,19 +2287,6 @@ struct sk_buff tcp_make_synack(struct sock sk, struct dst_entry *dst,
		TCPCB_FLAG_SYN \| TCPCB_FLAG_ACK);
		th->seq = htonl(TCP_SKB_CB(skb)->seq);
		th->ack_seq = htonl(tcp_rsk(req)->rcv_isn + 1);
		if (req->rcv_wnd == 0) { /* ignored for retransmitted syns */
		__u8 rcv_wscale;
		/* Set this up on the first call only */
		req->window_clamp = tp->window_clamp ? : dst_metric(dst, RTAX_WINDOW);
		/* tcp_full_space because it is guaranteed to be the first packet */
		tcp_select_initial_window(tcp_full_space(sk),
		dst_metric(dst, RTAX_ADVMSS) - (ireq->tstamp_ok ? TCPOLEN_TSTAMP_ALIGNED : 0),
		&req->rcv_wnd,
		&req->window_clamp,
		ireq->wscale_ok,
		&rcv_wscale);
		ireq->rcv_wscale = rcv_wscale;
		}

		/* RFC1323: The window in SYN & SYN/ACK segments is never scaled. */
		th->window = htons(min(req->rcv_wnd, 65535U));
		@@ -2244,18 +2295,7 @@ struct sk_buff tcp_make_synack(struct sock sk, struct dst_entry *dst,
		TCP_SKB_CB(skb)->when = cookie_init_timestamp(req);
		else
		#endif
		TCP_SKB_CB(skb)->when = tcp_time_stamp;
		tcp_syn_build_options((__be32 *)(th + 1), dst_metric(dst, RTAX_ADVMSS), ireq->tstamp_ok,
		ireq->sack_ok, ireq->wscale_ok, ireq->rcv_wscale,
		TCP_SKB_CB(skb)->when,
		req->ts_recent,
		(
		#ifdef CONFIG_TCP_MD5SIG
		md5 ? &md5_hash_location :
		#endif
		NULL)
		);

		tcp_options_write((__be32 *)(th + 1), tp, &opts, &md5_hash_location);
		th->doff = (tcp_header_size >> 2);
		TCP_INC_STATS(sock_net(sk), TCP_MIB_OUTSEGS);

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