mptcp: Handle MPTCP TCP options

Add hooks to parse and format the MP_CAPABLE option. This option is handled according to MPTCP version 0 (RFC6824). MPTCP version 1 MP_CAPABLE (RFC6824bis/RFC8684) will be added later in coordination with related code changes.

Peter Krystad committed 6 years ago

Commit eda7acd1 parent f870fa07 files · +181 −1Browse files

Unified · Split

7 files

include/linux/tcp.h +18 −0
include/net/mptcp.h +18 −0
net/ipv4/tcp_input.c +5 −0
net/ipv4/tcp_output.c +13 −0
net/mptcp/Makefile +1 −1
net/mptcp/options.c +97 −0
net/mptcp/protocol.h +29 −0

include/linux/tcp.h+18−0

@@ -78,6 +78,16 @@ struct tcp_sack_block { · 77 unmodified lines
78	78	#define TCP_SACK_SEEN (1 << 0) /1 = peer is SACK capable, /
79	79	#define TCP_DSACK_SEEN (1 << 2) /1 = DSACK was received from peer/
80	80
	81	+#if IS_ENABLED(CONFIG_MPTCP)
	82	+struct mptcp_options_received {
	83	+ u64 sndr_key;
	84	+ u64 rcvr_key;
	85	+ u8 mp_capable : 1,
	86	+ mp_join : 1,
	87	+ dss : 1;
	88	+};
	89	+#endif
	90	+
81	91	struct tcp_options_received {
82	92	/* PAWS/RTTM data */
83	93	int ts_recent_stamp;/* Time we stored ts_recent (for aging) */
@@ -95,6 +105,9 @@ struct tcp_options_received { · 11 unmodified lines
95	105	u8 num_sacks; /* Number of SACK blocks */
96	106	u16 user_mss; /* mss requested by user in ioctl */
97	107	u16 mss_clamp; /* Maximal mss, negotiated at connection setup */
	108	+#if IS_ENABLED(CONFIG_MPTCP)
	109	+ struct mptcp_options_received mptcp;
	110	+#endif
98	111	};
99	112
100	113	static inline void tcp_clear_options(struct tcp_options_received *rx_opt)
@@ -104,6 +117,11 @@ static inline void tcp_clear_options(struct tcp_options_received *rx_opt) · 3 unmodified lines
104	117	#if IS_ENABLED(CONFIG_SMC)
105	118	rx_opt->smc_ok = 0;
106	119	#endif
	120	+#if IS_ENABLED(CONFIG_MPTCP)
	121	+ rx_opt->mptcp.mp_capable = 0;
	122	+ rx_opt->mptcp.mp_join = 0;
	123	+ rx_opt->mptcp.dss = 0;
	124	+#endif
107	125	}
108	126
109	127	/* This is the max number of SACKS that we'll generate and process. It's safe

include/net/mptcp.h+18−0

@@ -9,6 +9,7 @@ · 8 unmodified lines
9	9	#define __NET_MPTCP_H
10	10
11	11	#include <linux/skbuff.h>
	12	+#include <linux/tcp.h>
12	13	#include <linux/types.h>
13	14
14	15	/* MPTCP sk_buff extension data */
@@ -26,10 +27,22 @@ struct mptcp_ext { · 11 unmodified lines
26	27	/* one byte hole */
27	28	};
28	29
	30	+struct mptcp_out_options {
	31	+#if IS_ENABLED(CONFIG_MPTCP)
	32	+ u16 suboptions;
	33	+ u64 sndr_key;
	34	+ u64 rcvr_key;
	35	+#endif
	36	+};
	37	+
29	38	#ifdef CONFIG_MPTCP
30	39
31	40	void mptcp_init(void);
32	41
	42	+void mptcp_parse_option(const unsigned char *ptr, int opsize,
	43	+ struct tcp_options_received *opt_rx);
	44	+void mptcp_write_options(__be32 ptr, struct mptcp_out_options opts);
	45	+
33	46	/* move the skb extension owership, with the assumption that 'to' is
34	47	* newly allocated
35	48	*/
@@ -76,6 +89,11 @@ static inline void mptcp_init(void) · 40 unmodified lines
76	89	{
77	90	}
78	91
	92	+static inline void mptcp_parse_option(const unsigned char *ptr, int opsize,
	93	+ struct tcp_options_received *opt_rx)
	94	+{
	95	+}
	96	+
79	97	static inline void mptcp_skb_ext_move(struct sk_buff *to,
80	98	const struct sk_buff *from)
81	99	{

net/ipv4/tcp_input.c+5−0

@@ -79,6 +79,7 @@ · 78 unmodified lines
79	79	#include <trace/events/tcp.h>
80	80	#include <linux/jump_label_ratelimit.h>
81	81	#include <net/busy_poll.h>
	82	+#include <net/mptcp.h>
82	83
83	84	int sysctl_tcp_max_orphans __read_mostly = NR_FILE;
84	85
@@ -3924,6 +3925,10 @@ void tcp_parse_options(const struct net *net, · 3839 unmodified lines
3924	3925	*/
3925	3926	break;
3926	3927	#endif
	3928	+ case TCPOPT_MPTCP:
	3929	+ mptcp_parse_option(ptr, opsize, opt_rx);
	3930	+ break;
	3931	+
3927	3932	case TCPOPT_FASTOPEN:
3928	3933	tcp_parse_fastopen_option(
3929	3934	opsize - TCPOLEN_FASTOPEN_BASE,

net/ipv4/tcp_output.c+13−0

@@ -38,6 +38,7 @@ · 37 unmodified lines
38	38	#define pr_fmt(fmt) "TCP: " fmt
39	39
40	40	#include <net/tcp.h>
	41	+#include <net/mptcp.h>
41	42
42	43	#include <linux/compiler.h>
43	44	#include <linux/gfp.h>
@@ -414,6 +415,7 @@ static inline bool tcp_urg_mode(const struct tcp_sock *tp) · 370 unmodified lines
414	415	#define OPTION_WSCALE (1 << 3)
415	416	#define OPTION_FAST_OPEN_COOKIE (1 << 8)
416	417	#define OPTION_SMC (1 << 9)
	418	+#define OPTION_MPTCP (1 << 10)
417	419
418	420	static void smc_options_write(__be32 ptr, u16 options)
419	421	{
@@ -439,8 +441,17 @@ struct tcp_out_options { · 19 unmodified lines
439	441	__u8 hash_location; / temporary pointer, overloaded */
440	442	__u32 tsval, tsecr; /* need to include OPTION_TS */
441	443	struct tcp_fastopen_cookie fastopen_cookie; / Fast open cookie */
	444	+ struct mptcp_out_options mptcp;
442	445	};
443	446
	447	+static void mptcp_options_write(__be32 ptr, struct tcp_out_options opts)
	448	+{
	449	+#if IS_ENABLED(CONFIG_MPTCP)
	450	+ if (unlikely(OPTION_MPTCP & opts->options))
	451	+ mptcp_write_options(ptr, &opts->mptcp);
	452	+#endif
	453	+}
	454	+
444	455	/* Write previously computed TCP options to the packet.
445	456	*
446	457	* Beware: Something in the Internet is very sensitive to the ordering of
@@ -549,6 +560,8 @@ static void tcp_options_write(__be32 ptr, struct tcp_sock tp, · 102 unmodified lines
549	560	}
550	561
551	562	smc_options_write(ptr, &options);
	563	+
	564	+ mptcp_options_write(ptr, opts);
552	565	}
553	566
554	567	static void smc_set_option(const struct tcp_sock *tp,

net/mptcp/Makefile+1−1

@@ -1,4 +1,4 @@
1	1	# SPDX-License-Identifier: GPL-2.0
2	2	obj-$(CONFIG_MPTCP) += mptcp.o
3	3
4		−mptcp-y := protocol.o
	4	+mptcp-y := protocol.o options.o

net/mptcp/options.c+97−0

@@ -0,0 +1,97 @@
	1	+// SPDX-License-Identifier: GPL-2.0
	2	+/* Multipath TCP
	3	+ *
	4	+ * Copyright (c) 2017 - 2019, Intel Corporation.
	5	+ */
	6	+
	7	+#include <linux/kernel.h>
	8	+#include <net/tcp.h>
	9	+#include <net/mptcp.h>
	10	+#include "protocol.h"
	11	+
	12	+void mptcp_parse_option(const unsigned char *ptr, int opsize,
	13	+ struct tcp_options_received *opt_rx)
	14	+{
	15	+ struct mptcp_options_received *mp_opt = &opt_rx->mptcp;
	16	+ u8 subtype = *ptr >> 4;
	17	+ u8 version;
	18	+ u8 flags;
	19	+
	20	+ switch (subtype) {
	21	+ case MPTCPOPT_MP_CAPABLE:
	22	+ if (opsize != TCPOLEN_MPTCP_MPC_SYN &&
	23	+ opsize != TCPOLEN_MPTCP_MPC_ACK)
	24	+ break;
	25	+
	26	+ version = *ptr++ & MPTCP_VERSION_MASK;
	27	+ if (version != MPTCP_SUPPORTED_VERSION)
	28	+ break;
	29	+
	30	+ flags = *ptr++;
	31	+ if (!((flags & MPTCP_CAP_FLAG_MASK) == MPTCP_CAP_HMAC_SHA1) \|\|
	32	+ (flags & MPTCP_CAP_EXTENSIBILITY))
	33	+ break;
	34	+
	35	+ /* RFC 6824, Section 3.1:
	36	+ * "For the Checksum Required bit (labeled "A"), if either
	37	+ * host requires the use of checksums, checksums MUST be used.
	38	+ * In other words, the only way for checksums not to be used
	39	+ * is if both hosts in their SYNs set A=0."
	40	+ *
	41	+ * Section 3.3.0:
	42	+ * "If a checksum is not present when its use has been
	43	+ * negotiated, the receiver MUST close the subflow with a RST as
	44	+ * it is considered broken."
	45	+ *
	46	+ * We don't implement DSS checksum - fall back to TCP.
	47	+ */
	48	+ if (flags & MPTCP_CAP_CHECKSUM_REQD)
	49	+ break;
	50	+
	51	+ mp_opt->mp_capable = 1;
	52	+ mp_opt->sndr_key = get_unaligned_be64(ptr);
	53	+ ptr += 8;
	54	+
	55	+ if (opsize == TCPOLEN_MPTCP_MPC_ACK) {
	56	+ mp_opt->rcvr_key = get_unaligned_be64(ptr);
	57	+ ptr += 8;
	58	+ pr_debug("MP_CAPABLE sndr=%llu, rcvr=%llu",
	59	+ mp_opt->sndr_key, mp_opt->rcvr_key);
	60	+ } else {
	61	+ pr_debug("MP_CAPABLE sndr=%llu", mp_opt->sndr_key);
	62	+ }
	63	+ break;
	64	+
	65	+ case MPTCPOPT_DSS:
	66	+ pr_debug("DSS");
	67	+ mp_opt->dss = 1;
	68	+ break;
	69	+
	70	+ default:
	71	+ break;
	72	+ }
	73	+}
	74	+
	75	+void mptcp_write_options(__be32 ptr, struct mptcp_out_options opts)
	76	+{
	77	+ if ((OPTION_MPTCP_MPC_SYN \|
	78	+ OPTION_MPTCP_MPC_ACK) & opts->suboptions) {
	79	+ u8 len;
	80	+
	81	+ if (OPTION_MPTCP_MPC_SYN & opts->suboptions)
	82	+ len = TCPOLEN_MPTCP_MPC_SYN;
	83	+ else
	84	+ len = TCPOLEN_MPTCP_MPC_ACK;
	85	+
	86	+ *ptr++ = htonl((TCPOPT_MPTCP << 24) \| (len << 16) \|
	87	+ (MPTCPOPT_MP_CAPABLE << 12) \|
	88	+ (MPTCP_SUPPORTED_VERSION << 8) \|
	89	+ MPTCP_CAP_HMAC_SHA1);
	90	+ put_unaligned_be64(opts->sndr_key, ptr);
	91	+ ptr += 2;
	92	+ if (OPTION_MPTCP_MPC_ACK & opts->suboptions) {
	93	+ put_unaligned_be64(opts->rcvr_key, ptr);
	94	+ ptr += 2;
	95	+ }
	96	+ }
	97	+}

net/mptcp/protocol.h+29−0

@@ -7,6 +7,35 @@ · 6 unmodified lines
7	7	#ifndef __MPTCP_PROTOCOL_H
8	8	#define __MPTCP_PROTOCOL_H
9	9
	10	+#define MPTCP_SUPPORTED_VERSION 0
	11	+
	12	+/* MPTCP option bits */
	13	+#define OPTION_MPTCP_MPC_SYN BIT(0)
	14	+#define OPTION_MPTCP_MPC_SYNACK BIT(1)
	15	+#define OPTION_MPTCP_MPC_ACK BIT(2)
	16	+
	17	+/* MPTCP option subtypes */
	18	+#define MPTCPOPT_MP_CAPABLE 0
	19	+#define MPTCPOPT_MP_JOIN 1
	20	+#define MPTCPOPT_DSS 2
	21	+#define MPTCPOPT_ADD_ADDR 3
	22	+#define MPTCPOPT_RM_ADDR 4
	23	+#define MPTCPOPT_MP_PRIO 5
	24	+#define MPTCPOPT_MP_FAIL 6
	25	+#define MPTCPOPT_MP_FASTCLOSE 7
	26	+
	27	+/* MPTCP suboption lengths */
	28	+#define TCPOLEN_MPTCP_MPC_SYN 12
	29	+#define TCPOLEN_MPTCP_MPC_SYNACK 12
	30	+#define TCPOLEN_MPTCP_MPC_ACK 20
	31	+
	32	+/* MPTCP MP_CAPABLE flags */
	33	+#define MPTCP_VERSION_MASK (0x0F)
	34	+#define MPTCP_CAP_CHECKSUM_REQD BIT(7)
	35	+#define MPTCP_CAP_EXTENSIBILITY BIT(6)
	36	+#define MPTCP_CAP_HMAC_SHA1 BIT(0)
	37	+#define MPTCP_CAP_FLAG_MASK (0x3F)
	38	+
10	39	/* MPTCP connection sock */
11	40	struct mptcp_sock {
12	41	/* inet_connection_sock must be the first member */