109 /* Calculate mss to advertise in SYN segment.
116  *    large MSS.
117  * 4. We do not make 3, we advertise MSS, calculated from first
120  * 5. Value 65535 for MSS is valid in IPv6 and means "as large as possible,
127 	int mss = tp->advmss;  in tcp_advertise_mss()  local
132 		if (metric < mss) {  in tcp_advertise_mss()
133 			mss = metric;  in tcp_advertise_mss()
134 			tp->advmss = mss;  in tcp_advertise_mss()
138 	return (__u16)mss;  in tcp_advertise_mss()
204  * be a multiple of mss if possible. We assume here that mss >= 1.
207 void tcp_select_initial_window(const struct sock *sk, int __space, __u32 mss,  in tcp_select_initial_window()  argument
220 	/* Quantize space offering to a multiple of mss if possible. */  in tcp_select_initial_window()
221 	if (space > mss)  in tcp_select_initial_window()
222 		space = rounddown(space, mss);  in tcp_select_initial_window()
238 		*rcv_wnd = min(*rcv_wnd, init_rcv_wnd * mss);  in tcp_select_initial_window()
448 	u16 mss;		/* 0 to disable */  member
676 	if (unlikely(opts->mss)) {  in tcp_options_write()
679 			       opts->mss);  in tcp_options_write()
836 	/* We always get an MSS option.  The option bytes which will be seen in  in tcp_syn_options()
837 	 * normal data packets should timestamps be used, must be in the MSS  in tcp_syn_options()
845 	opts->mss = tcp_advertise_mss(sk);  in tcp_syn_options()
899 				       unsigned int mss, struct sk_buff *skb,  in tcp_synack_options()  argument
926 	/* We always send an MSS option. */  in tcp_synack_options()
927 	opts->mss = mss;  in tcp_synack_options()
1254 		/* Original sch_fq does not pace first 10 MSS  in tcp_update_skb_after_send()
1336 		 * and in this case it is better to delay the delivery of 1-MSS  in __tcp_transmit_skb()
1749 /* Calculate MSS not accounting any TCP options.  */
1756 	/* Calculate base mss without TCP options:  in __tcp_mtu_to_mss()
1774 /* Calculate MSS. Not accounting for SACKs here.  */
1784 int tcp_mss_to_mtu(struct sock *sk, int mss)  in tcp_mss_to_mtu()  argument
1789 	return mss +  in tcp_mss_to_mtu()
1813 /* This function synchronize snd mss to current pmtu/exthdr set.
1815    tp->rx_opt.user_mss is mss set by user by TCP_MAXSEG. It does NOT counts
1818    tp->rx_opt.mss_clamp is mss negotiated at connection setup.
1819    It is minimum of user_mss and mss received with SYN.
1824    tp->mss_cache is current effective sending mss, including
1829    NOTE1. rfc1122 clearly states that advertised MSS
1857 /* Compute the current effective MSS, taking SACKs and IP options,
1969 /* Update snd_sml if this skb is under mss
1970  * Note that a TSO packet might end with a sub-mss segment
1972  * if ((skb->len % mss) != 0)
2068 	/* If last segment is not a full MSS, check if Nagle rules allow us  in tcp_mss_split_point()
2070 	 * Otherwise, we'll split the skb at last MSS boundary  in tcp_mss_split_point()
2322 		int mss = tcp_current_mss(sk);  in tcp_mtu_check_reprobe()  local
2329 		icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, mss);  in tcp_mtu_check_reprobe()
2542 	 * be resegmented into mss-sized pieces by tcp_write_xmit().  in tcp_mtu_probe()
2725  * snd_up-64k-mss .. snd_up cannot be large. However, taking into
2940 	int mss = tcp_current_mss(sk);  in tcp_send_loss_probe()  local
2948 	if (skb && tcp_snd_wnd_test(tp, skb, mss)) {  in tcp_send_loss_probe()
2950 		tcp_write_xmit(sk, mss, TCP_NAGLE_OFF, 2, GFP_ATOMIC);  in tcp_send_loss_probe()
2958 			  "invalid inflight: %u state %u cwnd %u mss %d\n",  in tcp_send_loss_probe()
2959 			  tp->packets_out, sk->sk_state, tcp_snd_cwnd(tp), mss);  in tcp_send_loss_probe()
2971 	if ((pcount > 1) && (skb->len > (pcount - 1) * mss)) {  in tcp_send_loss_probe()
2973 					  (pcount - 1) * mss, mss,  in tcp_send_loss_probe()
3038  *  RCV.BUFF - RCV.USER - RCV.WINDOW >= min(1/2 RCV.BUFF, MSS)"
3041  * it at least MSS bytes.
3057  *	space available and the free space is less than 1/2 mss,
3059  *	[ Actually, bsd uses MSS and 1/4 of maximal _window_ ]
3070  * multiple of MSS, at least until the free space gets quite small.
3076  * a multiple of the mss when it is feasible to do so.
3086 	/* MSS for the peer's data.  Previous versions used mss_clamp  in __tcp_select_window()
3088 	 * of peer's MSS is better for the performance.  It's more correct  in __tcp_select_window()
3092 	int mss = icsk->icsk_ack.rcv_mss;  in __tcp_select_window()  local
3102 	if (unlikely(mss > full_space)) {  in __tcp_select_window()
3103 		mss = full_space;  in __tcp_select_window()
3104 		if (mss <= 0)  in __tcp_select_window()
3127 		/* if free space is less than mss estimate, or is below 1/16th  in __tcp_select_window()
3131 		 * With large window, mss test triggers way too late in order  in __tcp_select_window()
3134 		if (free_space < (allowed_space >> 4) || free_space < mss)  in __tcp_select_window()
3142 	 * scaled window will not line up with the MSS boundary anyway.  in __tcp_select_window()
3149 		 * 1<<rcv_wscale > mss.  in __tcp_select_window()
3154 		/* Get the largest window that is a nice multiple of mss.  in __tcp_select_window()
3156 		 * If our current window offering is within 1 mss of the  in __tcp_select_window()
3162 		if (window <= free_space - mss || window > free_space)  in __tcp_select_window()
3163 			window = rounddown(free_space, mss);  in __tcp_select_window()
3164 		else if (mss == full_space &&  in __tcp_select_window()
3182 		if (free_space < (allowed_space >> 4) || free_space < mss ||  in __tcp_select_window()
3718 	int mss;  in tcp_make_synack()  local
3748 	mss = tcp_mss_clamp(tp, dst_metric_advmss(dst));  in tcp_make_synack()
3802 	tcp_header_size = tcp_synack_options(sk, req, mss, skb, &opts,  in tcp_make_synack()
3977 	tp->rx_opt.mss_clamp = tp->advmss;  /* If MSS is not cached */  in tcp_send_syn_data()
3981 	/* MSS for SYN-data is based on cached MSS and bounded by PMTU and  in tcp_send_syn_data()
3982 	 * user-MSS. Reserve maximum option space for middleboxes that add  in tcp_send_syn_data()
4332 		unsigned int mss = tcp_current_mss(sk);  in tcp_write_wakeup()  local
4343 		    skb->len > mss) {  in tcp_write_wakeup()
4344 			seg_size = min(seg_size, mss);  in tcp_write_wakeup()
4347 					 skb, seg_size, mss, GFP_ATOMIC))  in tcp_write_wakeup()
4350 			tcp_set_skb_tso_segs(skb, mss);  in tcp_write_wakeup()