From nobody Mon Sep 16 19:42:04 2024 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8D99A158D91 for ; Fri, 17 May 2024 17:41:10 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1715967670; cv=none; b=uK24jNOmKHCTbRP0CaV1OfDZW04jxKGTkBHNIC4dwvu/TSjKMQGLeUdlHKEDjPeFxhThrKzZxNb5RJuCCO5HDxr/h2fkfUUFcg2ftGVIbYjzxlefLFYKHpH+ZPsYW5MXgv9AB+/UGvnOSOLZc/Lt6dknCL4lS8ZLBhBCQU50SI8= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1715967670; c=relaxed/simple; bh=02UgC2SUUTf3R605TKQzX2uuRJeAOCEdWBzn15mij3s=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=ATbvJaFhA1ToU773m4Xck5kKnK3sm2NINObSIjOdEfPO6y4SARdoS39YsD2+nNcpVy1v+0U3vsARx7vwMNuMaWXV/I9/nkrvQnjMawlLyLJtvsRoBQdhmbvCFrGjcHt8bic2KG6UyHn7n646r2JXmJO0t+usyiSQXnvkmGlsYos= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=b4fVzLe+; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="b4fVzLe+" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6578EC32781; Fri, 17 May 2024 17:41:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1715967670; bh=02UgC2SUUTf3R605TKQzX2uuRJeAOCEdWBzn15mij3s=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=b4fVzLe+cNZLaor/QZLwwhTE2ZSkt0Ld3SYRfA2d46pIAdSgYTzg6wvXTi7wnnwBk eustfX7dxnqaaVdRiUF/Z0CWg/v+mFEqRM7NKioF+P5VFnX91l3LrD/W48GEPqqieM LRRpg5WU2cQExBc4rDpQ0yoeaWSvP24rg/SUu6NggYwSiyqgDxZlQUNxRHrkE6weBX MkJGefrp6/mcJD7/+aUbP5Vsuei1ONBCYZQHxm/x+adUjjeDVQnLOzlC0CmudKCsms 6qL2ms8k9onb/+E4ek3jWLThWmfaWTFhcJFdE2oc1V/lKmWk7FRKo9czoaSOqgemm2 uzrxNpZ34kh1Q== From: "Matthieu Baerts (NGI0)" Date: Fri, 17 May 2024 19:40:44 +0200 Subject: [PATCH mptcp-next 1/3] doc: mptcp: add missing 'available_schedulers' entry Precedence: bulk X-Mailing-List: mptcp@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20240517-mptcp-doc-v1-1-fc1ef063584e@kernel.org> References: <20240517-mptcp-doc-v1-0-fc1ef063584e@kernel.org> In-Reply-To: <20240517-mptcp-doc-v1-0-fc1ef063584e@kernel.org> To: mptcp@lists.linux.dev Cc: "Matthieu Baerts (NGI0)" X-Mailer: b4 0.13.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=937; i=matttbe@kernel.org; h=from:subject:message-id; bh=02UgC2SUUTf3R605TKQzX2uuRJeAOCEdWBzn15mij3s=; b=owEBbQKS/ZANAwAIAfa3gk9CaaBzAcsmYgBmR5az0pC17Sygq3x2ci/s3pn9t3GX3dzNKASpd G5Bkv+iWGGJAjMEAAEIAB0WIQToy4X3aHcFem4n93r2t4JPQmmgcwUCZkeWswAKCRD2t4JPQmmg cyqWD/4+GQ43YUKk+Vry1iZa/HUe2KGzfiIV2JjDCye3tzmnfareG/gFt1sW5HqPn2O8iAWBJR5 TWzxC+6x6y1KZhehBgefAb6gw4vX7crQrxAf6O13DCFMtGfwzUxFRRLPTsb/zqdgpTpLfX6N2Mv i9sv5m3yVnuoiL9igmb7W38kq6+91bccB/76GGyebc2j8E93tQS4uXJW8k5DyOHdnNrriZD1yr2 aUpMTU6cVgLfaDUQ/fzMiyi1EzQERK0DOqiXAiR/+LOM7M+qz6VrE2cQV5U2METSEnxDzZkx88v 5swqOpQnldAm6O65yNyGqjqG/3AGTYyej5wbfzBrcqrPK1f8F56hv93e6ZB4whbnbDkv547aPgs 8l4uQV2CJYUAXltzvwfFstgmtB/uP0Q5Rtu67netOwhMAkPCtNhstE/QBId9fGBiOcPGop9WikD ZRh7AoYYSjHSmEr2bV/R4mVBSiHQn01ZvUUSMy39iw8CQT2ECXmIO0akjk+9h1p7oumUktBYMbf n8UnSTmhpnlqhjVj8/IXFRxiOWt/6rFn36JZX0nYt+bHXPjjBzWlELOpPN1S/FQGePOrkMm1v/n frKyYaCiVU67YoRs5so5uPUqbfRocD6DSjg4CzeXwzjgHtOZExiSe7Jk86FJrMggONs+p7/lU4J th1ebdGCRZ3Mc8Q== X-Developer-Key: i=matttbe@kernel.org; a=openpgp; fpr=E8CB85F76877057A6E27F77AF6B7824F4269A073 This sysctl knob has been added recently, but the documentation has not been updated. This knob is used to show the available schedulers choices that are registered, similar to 'net.ipv4.tcp_available_congestion_control'. Fixes: 73c900aa3660 ("mptcp: add net.mptcp.available_schedulers") Signed-off-by: Matthieu Baerts (NGI0) Reviewed-by: Mat Martineau --- Documentation/networking/mptcp-sysctl.rst | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/Documentation/networking/mptcp-sysctl.rst b/Documentation/netw= orking/mptcp-sysctl.rst index 69975ce25a02..102a45e7bfa8 100644 --- a/Documentation/networking/mptcp-sysctl.rst +++ b/Documentation/networking/mptcp-sysctl.rst @@ -93,3 +93,7 @@ scheduler - STRING sysctl. =20 Default: "default" + +available_schedulers - STRING + Shows the available schedulers choices that are registered. More packet + schedulers may be available, but not loaded. --=20 2.43.0 From nobody Mon Sep 16 19:42:04 2024 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C2058158D7E for ; Fri, 17 May 2024 17:41:11 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1715967671; cv=none; b=FIr+7Gx0gf32TZn3hj2vquvprmv9vct4SxRwIYKQ0QdgaQaZumcRLBEG98P+LOkx+OlEsl/2qwEVDFrij0botWvezgKe/buKNipjsQRLF7jNpEK9T5Fl49/WmX8lfsUfKBb+Epa5mZSjV894qL4nKwIOV13/Kdlwt/JI5aiuZmY= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1715967671; c=relaxed/simple; bh=3gm2Uf9xQQmepglmxe6UbEr1eW1MN3QblnjEz01QPfI=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=GTHYskuHVOP5nVpUU4pDrZTf15dDgIwFRxxpw8IkRZ8V7tExw9onBs298mdbpAg892PAjfrlwLhk8EV8cmFZThdxXszgkOhNfc8oKL4jsqWSPE9kdRnqvVpSkm5NBA5uPic+UnWisq8F6dnagSvRkmvcqMk7QAbNMxhK8IS6YFI= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=t+osDyjI; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="t+osDyjI" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B4774C2BD10; Fri, 17 May 2024 17:41:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1715967671; bh=3gm2Uf9xQQmepglmxe6UbEr1eW1MN3QblnjEz01QPfI=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=t+osDyjIiV8EDH0XqbnwUx+1X07QmD9OHUblgFLtoRVBDKHGlhD5IJrS9JFl7DCWf lbzKZmQUsydBfBuravkILGv5xsiU8aRWWHmOhDapzukKtdaj4ijHdV9CYc3t/Ez8Aa +/wCfv19xqEpoy6hf9xMaqwqvB3X+WJj210k/X3UsxtEg1RiSiK6PUYWfX/7ZYK1RJ 8hom34QpavDcJDf1MohAKkVxOtgxk7A9AVZQthIPD08jX5Abquv88eHsyssvnT89O/ SSewNUoDdhH1x+ujs7drX+Wix6/3rCZ0ywmWFc0AVqx2XSvjM5jZhwVWLd58cb/EDi 9gJEqK/Rv6tNQ== From: "Matthieu Baerts (NGI0)" Date: Fri, 17 May 2024 19:40:45 +0200 Subject: [PATCH mptcp-next 2/3] doc: mptcp: alphabetical order Precedence: bulk X-Mailing-List: mptcp@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20240517-mptcp-doc-v1-2-fc1ef063584e@kernel.org> References: <20240517-mptcp-doc-v1-0-fc1ef063584e@kernel.org> In-Reply-To: <20240517-mptcp-doc-v1-0-fc1ef063584e@kernel.org> To: mptcp@lists.linux.dev Cc: "Matthieu Baerts (NGI0)" X-Mailer: b4 0.13.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=3857; i=matttbe@kernel.org; h=from:subject:message-id; bh=3gm2Uf9xQQmepglmxe6UbEr1eW1MN3QblnjEz01QPfI=; b=owEBbQKS/ZANAwAIAfa3gk9CaaBzAcsmYgBmR5azL4eAYqSG0mHxCuRgp9cgM12e+P1e/vLe4 b4HKwDAAhGJAjMEAAEIAB0WIQToy4X3aHcFem4n93r2t4JPQmmgcwUCZkeWswAKCRD2t4JPQmmg c2nFD/45GeCn8FCK92968ZUbYh9tsfJxarLrK+08Mgk6VPY9vgxYc3ZrOJvtE3oJj0FZamguLzF okPVdvq5V9kziu8jMb2KLVZb10T/OGwDK0W2vhfgG3XhkNBg+5kb/Fih6J/gDRBCjj7ane3xMrV KNahVUkOINDy+LMtVnJOxZivP0I9HCV9Rl7hKlEpQEFORObuxIdWKJa2+MksxD2VqNgj7GDCUux FovXvTalxdJOUVKo18DWVnn4RqBW7RHpT21wotJYoNgvw6T6xMi/pEOz2VfmfGScb0kqY9ldd5n NFhxI/uvHtaQGBSO9v5w76IrJrGJpor3RWfU2AfNUboWKnjCdEmuvAVhoplB6EfrhCyShX+nluo A6Plwjjw+3P1X8rEVE5VcB5qNdPPSKe99avXD6/i3WqGkZ2YJBdQ3ws9MZ7mj61dSheO53d3dyN X88JPttPRsf/kGvdr2QvOOn/lPddXex2wsTiRae9yGQeYQDuJbkeFsRaxhV2R3GykJh0xGRAv7z Jl7zTOipxQUZIB+SYANMHxN3DeznB0Pcwd9poZqQ2qB35PceYyLd+UABZ2NYvOb5xikAPIHboji +JYK87BZoyA8d2BndyCc9+QGrFYb934xDp02bkjr7821FyEGz1lgzDLJd+vMPhWR3nFTomfpdlZ 1m+BZUIBkMbuZGg== X-Developer-Key: i=matttbe@kernel.org; a=openpgp; fpr=E8CB85F76877057A6E27F77AF6B7824F4269A073 Similar to what is done in other 'sysctl' pages. Also, by not putting new entries at the end, this can help to reduce conflicts in case of backports. Signed-off-by: Matthieu Baerts (NGI0) Reviewed-by: Mat Martineau --- Documentation/networking/mptcp-sysctl.rst | 78 +++++++++++++++------------= ---- 1 file changed, 39 insertions(+), 39 deletions(-) diff --git a/Documentation/networking/mptcp-sysctl.rst b/Documentation/netw= orking/mptcp-sysctl.rst index 102a45e7bfa8..fd514bba8c43 100644 --- a/Documentation/networking/mptcp-sysctl.rst +++ b/Documentation/networking/mptcp-sysctl.rst @@ -7,14 +7,6 @@ MPTCP Sysfs variables /proc/sys/net/mptcp/* Variables =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D =20 -enabled - BOOLEAN - Control whether MPTCP sockets can be created. - - MPTCP sockets can be created if the value is 1. This is a - per-namespace sysctl. - - Default: 1 (enabled) - add_addr_timeout - INTEGER (seconds) Set the timeout after which an ADD_ADDR control message will be resent to an MPTCP peer that has not acknowledged a previous @@ -25,25 +17,6 @@ add_addr_timeout - INTEGER (seconds) =20 Default: 120 =20 -close_timeout - INTEGER (seconds) - Set the make-after-break timeout: in absence of any close or - shutdown syscall, MPTCP sockets will maintain the status - unchanged for such time, after the last subflow removal, before - moving to TCP_CLOSE. - - The default value matches TCP_TIMEWAIT_LEN. This is a per-namespace - sysctl. - - Default: 60 - -checksum_enabled - BOOLEAN - Control whether DSS checksum can be enabled. - - DSS checksum can be enabled if the value is nonzero. This is a - per-namespace sysctl. - - Default: 0 - allow_join_initial_addr_port - BOOLEAN Allow peers to send join requests to the IP address and port number used by the initial subflow if the value is 1. This controls a flag that is @@ -57,6 +30,37 @@ allow_join_initial_addr_port - BOOLEAN =20 Default: 1 =20 +available_schedulers - STRING + Shows the available schedulers choices that are registered. More packet + schedulers may be available, but not loaded. + +checksum_enabled - BOOLEAN + Control whether DSS checksum can be enabled. + + DSS checksum can be enabled if the value is nonzero. This is a + per-namespace sysctl. + + Default: 0 + +close_timeout - INTEGER (seconds) + Set the make-after-break timeout: in absence of any close or + shutdown syscall, MPTCP sockets will maintain the status + unchanged for such time, after the last subflow removal, before + moving to TCP_CLOSE. + + The default value matches TCP_TIMEWAIT_LEN. This is a per-namespace + sysctl. + + Default: 60 + +enabled - BOOLEAN + Control whether MPTCP sockets can be created. + + MPTCP sockets can be created if the value is 1. This is a + per-namespace sysctl. + + Default: 1 (enabled) + pm_type - INTEGER Set the default path manager type to use for each new MPTCP socket. In-kernel path management will control subflow @@ -74,6 +78,14 @@ pm_type - INTEGER =20 Default: 0 =20 +scheduler - STRING + Select the scheduler of your choice. + + Support for selection of different schedulers. This is a per-namespace + sysctl. + + Default: "default" + stale_loss_cnt - INTEGER The number of MPTCP-level retransmission intervals with no traffic and pending outstanding data on a given subflow required to declare it stale. @@ -85,15 +97,3 @@ stale_loss_cnt - INTEGER This is a per-namespace sysctl. =20 Default: 4 - -scheduler - STRING - Select the scheduler of your choice. - - Support for selection of different schedulers. This is a per-namespace - sysctl. - - Default: "default" - -available_schedulers - STRING - Shows the available schedulers choices that are registered. 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Most of what is there comes from our recently updated mptcp.dev website, with additional links to resources from the kernel documentation. This is a first version, mainly targeting app developers and users. Link: https://www.mptcp.dev Signed-off-by: Matthieu Baerts (NGI0) Reviewed-by: Mat Martineau --- Documentation/networking/index.rst | 1 + Documentation/networking/mptcp.rst | 155 +++++++++++++++++++++++++++++++++= ++++ MAINTAINERS | 2 +- 3 files changed, 157 insertions(+), 1 deletion(-) diff --git a/Documentation/networking/index.rst b/Documentation/networking/= index.rst index 7664c0bfe461..a6443851a142 100644 --- a/Documentation/networking/index.rst +++ b/Documentation/networking/index.rst @@ -72,6 +72,7 @@ Contents: mac80211-injection mctp mpls-sysctl + mptcp mptcp-sysctl multiqueue multi-pf-netdev diff --git a/Documentation/networking/mptcp.rst b/Documentation/networking/= mptcp.rst new file mode 100644 index 000000000000..cb04a553d010 --- /dev/null +++ b/Documentation/networking/mptcp.rst @@ -0,0 +1,155 @@ +.. SPDX-License-Identifier: GPL-2.0 + +=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D +Multipath TCP (MPTCP) +=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D + +Introduction +=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D + +Multipath TCP or MPTCP is an extension to the standard TCP and is describe= d in +`RFC 8684 (MPTCPv1) `_. It al= lows a +device to make use of multiple interfaces at once to send and receive TCP +packets over a single MPTCP connection. MPTCP can aggregate the bandwidth = of +multiple interfaces or prefer the one with the lowest latency, it also all= ows a +fail-over if one path is down, and the traffic is seamlessly reinjected on= other +paths. + +For more details about Multipath TCP in the Linux kernel, please see the +official website: `mptcp.dev `. + + +Use cases +=3D=3D=3D=3D=3D=3D=3D=3D=3D + +Thanks to MPTCP, being able to use multiple paths in parallel or simultane= ously +brings new use-cases, compared to TCP: + +- Seamless handovers: switching from one path to another while preserving + established connections, e.g. to be used in mobility use-cases, like on + smartphones. +- Best network selection: using the "best" available path depending on some + conditions, e.g. latency, losses, cost, bandwidth, etc. +- Network aggregation: using multiple paths at the same time to have a hig= her + throughput, e.g. to combine fixed and mobile networks to send files fast= er. + + +Concepts +=3D=3D=3D=3D=3D=3D=3D=3D + +Technically, when a new socket is created with the ``IPPROTO_MPTCP`` proto= col +(Linux-specific), a *subflow* (or *path*) is created. This *subflow* consi= sts of +a regular TCP connection that is used to transmit data through one interfa= ce. +Additional *subflows* can be negotiated later between the hosts. For the r= emote +host to be able to detect the use of MPTCP, a new field is added to the TCP +*option* field of the underlying TCP *subflow*. This field contains, among= st +other things, a ``MP_CAPABLE`` option that tells the other host to use MPT= CP if +it is supported. If the remote host or any middlebox in between does not s= upport +it, the returned ``SYN+ACK`` packet will not contain MPTCP options in the = TCP +*option* field. In that case, the connection will be "downgraded" to plain= TCP, +and it will continue with a single path. + +This behavior is made possible by two internal components: the path manage= r, and +the packet scheduler. + +Path Manager +------------ + +The Path Manager is in charge of *subflows*, from creation to deletion, an= d also +address announcements. Typically, it is the client side that initiates sub= flows, +and the server side that announces additional addresses via the ``ADD_ADDR= `` and +``REMOVE_ADDR`` options. + +Path managers are controlled by the ``net.mptcp.pm_type`` sysctl knob -- s= ee +mptcp-sysctl.rst. There are two types: the in-kernel one (type ``0``) wher= e the +same rules are applied for all the connections (see: ``ip mptcp``) ; and t= he +userspace one (type ``1``), controlled by a userspace daemon (i.e. `mptcpd +`_) where different rules can be applied for ea= ch +connection. The path managers can be controlled via a Netlink API, see +netlink_spec/mptcp_pm.rst. + +To be able to use multiple IP addresses on a host to create multiple *subf= lows* +(paths), the default in-kernel MPTCP path-manager needs to know which IP +addresses can be used. This can be configured with ``ip mptcp endpoint`` f= or +example. + +Packet Scheduler +---------------- + +The Packet Scheduler is in charge of selecting which available *subflow(s)= * to +use to send the next data packet. It can decide to maximize the use of the +available bandwidth, only to pick the path with the lower latency, or any = other +policy depending on the configuration. + +Packet schedulers are controlled by the ``net.mptcp.scheduler`` sysctl kno= b -- +see mptcp-sysctl.rst. + + +Sockets API +=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D + +Creating MPTCP sockets +---------------------- + +On Linux, MPTCP can be used by selecting MPTCP instead of TCP when creatin= g the +``socket``: + +.. code-block:: C + + int sd =3D socket(AF_INET(6), SOCK_STREAM, IPPROTO_MPTCP); + +Note that ``IPPROTO_MPTCP`` is defined as ``262``. + +If MPTCP is not supported, ``errno`` will be set to: + +- ``EINVAL``: (*Invalid argument*): MPTCP is not available, on kernels < 5= .6. +- ``EPROTONOSUPPORT`` (*Protocol not supported*): MPTCP has not been compi= led, + on kernels >=3D v5.6. +- ``ENOPROTOOPT`` (*Protocol not available*): MPTCP has been disabled using + ``net.mptcp.enabled`` sysctl knob, see mptcp-sysctl.rst. + +MPTCP is then opt-in: applications need to explicitly request it. Note that +applications can be forced to use MPTCP with different techniques, e.g. +``LD_PRELOAD`` (see ``mptcpize``), eBPF (see ``mptcpify``), SystemTAP, +``GODEBUG`` (``GODEBUG=3Dmultipathtcp=3D1``), etc. + +Switching to ``IPPROTO_MPTCP`` instead of ``IPPROTO_TCP`` should be as +transparent as possible for the userspace applications. + +Socket options +-------------- + +MPTCP supports most socket options handled by TCP. It is possible some less +common ones are not supported, but contributions are welcomed. + +Generally, the same value is propagated to all subflows, including the ones +created later. eBPF can be used to set different values per subflows. + +There are some MPTCP specific socket options at the ``SOL_MPTCP`` (284) le= vel to +retrieve info. They fill the ``optval`` buffer of the ``getsockopt()`` sys= tem +call: + +- ``MPTCP_INFO``: Uses ``struct mptcp_info``. +- ``MPTCP_TCPINFO``: Uses ``struct mptcp_subflow_data``, followed by an ar= ray of + ``struct tcp_info``. +- ``MPTCP_SUBFLOW_ADDRS``: Uses ``struct mptcp_subflow_data``, followed by= an + array of ``mptcp_subflow_addrs``. +- ``MPTCP_FULL_INFO``: Uses ``struct mptcp_full_info``, with one pointer t= o an + array of ``struct mptcp_subflow_info`` (including the + ``struct mptcp_subflow_addrs``), and one pointer to an array of + ``struct tcp_info``, followed by the content of ``struct mptcp_info``. + +Note that at the TCP level, ``TCP_IS_MPTCP`` socket option can be used to = know +if MPTCP is still being used: the value will be set to 1 if it is. + + +Design choices +=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D + +A new socket type has been added for MPTCP for the userspace-facing socket= . The +kernel is in charge of creating subflow sockets: they are TCP sockets wher= e the +behavior is modified using TCP-ULP. + +MPTCP listen sockets will create "plain" *accepted* TCP sockets if the +connection request from the client didn't ask for MPTCP, making the perfor= mance +impact minimal when MPTCP is enabled by default. diff --git a/MAINTAINERS b/MAINTAINERS index 50892cdafb25..4edd8a3742f0 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -15573,7 +15573,7 @@ B: https://github.com/multipath-tcp/mptcp_net-next/= issues T: git https://github.com/multipath-tcp/mptcp_net-next.git export-net T: git https://github.com/multipath-tcp/mptcp_net-next.git export F: Documentation/netlink/specs/mptcp_pm.yaml -F: Documentation/networking/mptcp-sysctl.rst +F: Documentation/networking/mptcp*.rst F: include/net/mptcp.h F: include/trace/events/mptcp.h F: include/uapi/linux/mptcp*.h --=20 2.43.0