From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Anatoly Sivov" Subject: tcp_mtu_probe implementation details Date: Tue, 20 Dec 2011 22:31:34 +0400 Message-ID: Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=mail.ru; s=mail; h=Message-ID:From:Content-Transfer-Encoding:MIME-Version:Subject:To:Date:Content-Type; bh=Oo7nQJcMia+UYtbfyv3XzvctW0ypXWmWKy07j0QAAcg=; b=LDuzcd9jSBhuJecP8ndaVqzcEsDrSCz6DVm8wDOlDq8DLwRnU+moB3xz/XY5C986/K/ekH7Mxx6Q9AQKQ5qQU7PC6jhLBgBkQjNyP5aMViKvmxP33d9wXgyoL1SCs6TV; Sender: linux-newbie-owner@vger.kernel.org List-ID: Content-Type: text/plain; charset="us-ascii"; format="flowed"; delsp="yes" To: linux-newbie@vger.kernel.org Hi all, Looking on TCP implementation in Linux I see that there are some things that I don't understand in tcp_mtu_probe() implementation. Could someone clear them for me or share the link to Linux PMTUD documentation, please? The first thing I don't understand is tp->snd_cwnd < 11 in if (!icsk->icsk_mtup.enabled || icsk->icsk_mtup.probe_size || inet_csk(sk)->icsk_ca_state != TCP_CA_Open || tp->snd_cwnd < 11 || tp->rx_opt.num_sacks || tp->rx_opt.dsack) return -1; What is magic number "11" here? The other question is about size_needed variable. It is assigned to value probe_size + (tp->reordering + 1) * tp->mss_cache And that is not clear for me. What is this "(tp->reordering + 1) * tp->mss_cache" addition? Thanks. -- To unsubscribe from this list: send the line "unsubscribe linux-newbie" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.linux-learn.org/faqs