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Commit bee7ca9e authored by William Allen Simpson's avatar William Allen Simpson Committed by David S. Miller
Browse files

net: TCP_MSS_DEFAULT, TCP_MSS_DESIRED 



Define two symbols needed in both kernel and user space.

Remove old (somewhat incorrect) kernel variant that wasn't used in
most cases.  Default should apply to both RMSS and SMSS (RFC2581).

Replace numeric constants with defined symbols.

Stand-alone patch, originally developed for TCPCT.

Signed-off-by: default avatar <William.Allen.Simpson@gmail.com>
Acked-by: default avatarEric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent cbbef5e1

include/linux/tcp.h

+6 −0
Original line number Original line Diff line number Diff line
@@ -81,6 +81,12 @@ enum { 
	TCP_DATA_OFFSET = __cpu_to_be32(0xF0000000)

	TCP_DATA_OFFSET = __cpu_to_be32(0xF0000000)

}; 

}; 





/*

 * TCP general constants

 */

#define TCP_MSS_DEFAULT		 536U	/* IPv4 (RFC1122, RFC2581) */

#define TCP_MSS_DESIRED		1220U	/* IPv6 (tunneled), EDNS0 (RFC3226) */



/* TCP socket options */

/* TCP socket options */

#define TCP_NODELAY		1	/* Turn off Nagle's algorithm. */

#define TCP_NODELAY		1	/* Turn off Nagle's algorithm. */

#define TCP_MAXSEG		2	/* Limit MSS */

#define TCP_MAXSEG		2	/* Limit MSS */

include/net/tcp.h

+0 −3
Original line number Original line Diff line number Diff line
@@ -62,9 +62,6 @@ extern void tcp_time_wait(struct sock *sk, int state, int timeo); 
/* Minimal accepted MSS. It is (60+60+8) - (20+20). */

/* Minimal accepted MSS. It is (60+60+8) - (20+20). */

#define TCP_MIN_MSS		88U

#define TCP_MIN_MSS		88U





/* Minimal RCV_MSS. */

#define TCP_MIN_RCVMSS		536U



/* The least MTU to use for probing */

/* The least MTU to use for probing */

#define TCP_BASE_MSS		512

#define TCP_BASE_MSS		512

net/ipv4/tcp_input.c

+2 −2
Original line number Original line Diff line number Diff line
@@ -140,7 +140,7 @@ static void tcp_measure_rcv_mss(struct sock *sk, const struct sk_buff *skb) 
		 * "len" is invariant segment length, including TCP header.

		 * "len" is invariant segment length, including TCP header.

		 */

		 */

		len += skb->data - skb_transport_header(skb);

		len += skb->data - skb_transport_header(skb);

		if (len >= TCP_MIN_RCVMSS + sizeof(struct tcphdr) ||

		if (len >= TCP_MSS_DEFAULT + sizeof(struct tcphdr) ||

		    /* If PSH is not set, packet should be

		    /* If PSH is not set, packet should be

		     * full sized, provided peer TCP is not badly broken.

		     * full sized, provided peer TCP is not badly broken.

		     * This observation (if it is correct 8)) allows

		     * This observation (if it is correct 8)) allows
@@ -411,7 +411,7 @@ void tcp_initialize_rcv_mss(struct sock *sk) 
	unsigned int hint = min_t(unsigned int, tp->advmss, tp->mss_cache);

	unsigned int hint = min_t(unsigned int, tp->advmss, tp->mss_cache);





	hint = min(hint, tp->rcv_wnd / 2);

	hint = min(hint, tp->rcv_wnd / 2);

	hint = min(hint, TCP_MIN_RCVMSS);

	hint = min(hint, TCP_MSS_DEFAULT);

	hint = max(hint, TCP_MIN_MSS);

	hint = max(hint, TCP_MIN_MSS);





	inet_csk(sk)->icsk_ack.rcv_mss = hint;

	inet_csk(sk)->icsk_ack.rcv_mss = hint;

net/ipv4/tcp_ipv4.c

+3 −3
Original line number Original line Diff line number Diff line
@@ -217,7 +217,7 @@ int tcp_v4_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len) 
	if (inet->opt)

	if (inet->opt)

		inet_csk(sk)->icsk_ext_hdr_len = inet->opt->optlen;

		inet_csk(sk)->icsk_ext_hdr_len = inet->opt->optlen;





	tp->rx_opt.mss_clamp = 536;

	tp->rx_opt.mss_clamp = TCP_MSS_DEFAULT;





	/* Socket identity is still unknown (sport may be zero).

	/* Socket identity is still unknown (sport may be zero).

	 * However we set state to SYN-SENT and not releasing socket

	 * However we set state to SYN-SENT and not releasing socket
@@ -1268,7 +1268,7 @@ int tcp_v4_conn_request(struct sock *sk, struct sk_buff *skb) 
		goto drop_and_free;

		goto drop_and_free;





	tcp_clear_options(&tmp_opt);

	tcp_clear_options(&tmp_opt);

	tmp_opt.mss_clamp = 536;

	tmp_opt.mss_clamp = TCP_MSS_DEFAULT;

	tmp_opt.user_mss  = tcp_sk(sk)->rx_opt.user_mss;

	tmp_opt.user_mss  = tcp_sk(sk)->rx_opt.user_mss;





	tcp_parse_options(skb, &tmp_opt, 0, dst);

	tcp_parse_options(skb, &tmp_opt, 0, dst);
@@ -1815,7 +1815,7 @@ static int tcp_v4_init_sock(struct sock *sk) 
	 */

	 */

	tp->snd_ssthresh = TCP_INFINITE_SSTHRESH;

	tp->snd_ssthresh = TCP_INFINITE_SSTHRESH;

	tp->snd_cwnd_clamp = ~0;

	tp->snd_cwnd_clamp = ~0;

	tp->mss_cache = 536;

	tp->mss_cache = TCP_MSS_DEFAULT;





	tp->reordering = sysctl_tcp_reordering;

	tp->reordering = sysctl_tcp_reordering;

	icsk->icsk_ca_ops = &tcp_init_congestion_ops;

	icsk->icsk_ca_ops = &tcp_init_congestion_ops;

net/ipv4/tcp_minisocks.c

+1 −1
Original line number Original line Diff line number Diff line
@@ -476,7 +476,7 @@ struct sock *tcp_create_openreq_child(struct sock *sk, struct request_sock *req, 
		if (newtp->af_specific->md5_lookup(sk, newsk))

		if (newtp->af_specific->md5_lookup(sk, newsk))

			newtp->tcp_header_len += TCPOLEN_MD5SIG_ALIGNED;

			newtp->tcp_header_len += TCPOLEN_MD5SIG_ALIGNED;

#endif

#endif

		if (skb->len >= TCP_MIN_RCVMSS+newtp->tcp_header_len)

		if (skb->len >= TCP_MSS_DEFAULT + newtp->tcp_header_len)

			newicsk->icsk_ack.last_seg_size = skb->len - newtp->tcp_header_len;

			newicsk->icsk_ack.last_seg_size = skb->len - newtp->tcp_header_len;

		newtp->rx_opt.mss_clamp = req->mss;

		newtp->rx_opt.mss_clamp = req->mss;

		TCP_ECN_openreq_child(newtp, req);

		TCP_ECN_openreq_child(newtp, req);