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Date: Tue, 2 Mar 2010 15:16:59 +1100
From: Simon Horman <horms@...ge.net.au>
To: William Allen Simpson <william.allen.simpson@...il.com>
Cc: Linux Kernel Network Developers <netdev@...r.kernel.org>
Subject: Re: [PATCH] net: TCP_MSS_DEFAULT, TCP_MSS_DESIRED
On Tue, Nov 10, 2009 at 02:51:18PM -0500, William Allen Simpson wrote:
> 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).
The name was somewhat incorrect in the sense that it was named
differently in the RFCs?
> Replace numeric constants with defined symbols.
That bit sounds very reasonable.
> Stand-alone patch, originally developed for TCPCT.
>
> Signed-off-by: William.Allen.Simpson@...il.com
> Acked-by: Eric Dumazet <eric.dumazet@...il.com>
> ---
> include/linux/tcp.h | 6 ++++++
> include/net/tcp.h | 3 ---
> net/ipv4/tcp_input.c | 4 ++--
> net/ipv4/tcp_ipv4.c | 6 +++---
> net/ipv4/tcp_minisocks.c | 2 +-
> net/ipv6/tcp_ipv6.c | 2 +-
> 6 files changed, 13 insertions(+), 10 deletions(-)
> diff --git a/include/linux/tcp.h b/include/linux/tcp.h
> index eeecb85..32d7d77 100644
> --- a/include/linux/tcp.h
> +++ b/include/linux/tcp.h
> @@ -81,6 +81,12 @@ enum {
> 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) */
Are you planing to use TCP_MSS_DESIRED anywhere?
> +
> /* TCP socket options */
> #define TCP_NODELAY 1 /* Turn off Nagle's algorithm. */
> #define TCP_MAXSEG 2 /* Limit MSS */
> diff --git a/include/net/tcp.h b/include/net/tcp.h
> index 25bf3ba..a413e9f 100644
> --- a/include/net/tcp.h
> +++ b/include/net/tcp.h
> @@ -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). */
> #define TCP_MIN_MSS 88U
>
> -/* Minimal RCV_MSS. */
> -#define TCP_MIN_RCVMSS 536U
> -
> /* The least MTU to use for probing */
> #define TCP_BASE_MSS 512
>
> diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
> index be0c5bf..cc306ac 100644
> --- a/net/ipv4/tcp_input.c
> +++ b/net/ipv4/tcp_input.c
> @@ -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 += 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
> * full sized, provided peer TCP is not badly broken.
> * 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);
>
> 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);
>
> inet_csk(sk)->icsk_ack.rcv_mss = hint;
> diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
> index f83ac91..0718fde 100644
> --- a/net/ipv4/tcp_ipv4.c
> +++ b/net/ipv4/tcp_ipv4.c
> @@ -217,7 +217,7 @@ int tcp_v4_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len)
> if (inet->opt)
> 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).
> * However we set state to SYN-SENT and not releasing socket
> @@ -1270,7 +1270,7 @@ int tcp_v4_conn_request(struct sock *sk, struct sk_buff *skb)
> goto drop_and_free;
>
> 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;
>
> tcp_parse_options(skb, &tmp_opt, 0, dst);
> @@ -1818,7 +1818,7 @@ static int tcp_v4_init_sock(struct sock *sk)
> */
> tp->snd_ssthresh = TCP_INFINITE_SSTHRESH;
> tp->snd_cwnd_clamp = ~0;
> - tp->mss_cache = 536;
> + tp->mss_cache = TCP_MSS_DEFAULT;
>
> tp->reordering = sysctl_tcp_reordering;
> icsk->icsk_ca_ops = &tcp_init_congestion_ops;
> diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c
> index fb68bab..7a42990 100644
> --- a/net/ipv4/tcp_minisocks.c
> +++ b/net/ipv4/tcp_minisocks.c
> @@ -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))
> newtp->tcp_header_len += TCPOLEN_MD5SIG_ALIGNED;
> #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;
> newtp->rx_opt.mss_clamp = req->mss;
> TCP_ECN_openreq_child(newtp, req);
> diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
> index 6951827..b528f75 100644
> --- a/net/ipv6/tcp_ipv6.c
> +++ b/net/ipv6/tcp_ipv6.c
> @@ -1849,7 +1849,7 @@ static int tcp_v6_init_sock(struct sock *sk)
> */
> tp->snd_ssthresh = TCP_INFINITE_SSTHRESH;
> tp->snd_cwnd_clamp = ~0;
> - tp->mss_cache = 536;
> + tp->mss_cache = TCP_MSS_DEFAULT;
>
> tp->reordering = sysctl_tcp_reordering;
>
> --
> 1.6.3.3
>
--
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