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// SPDX-License-Identifier: GPL-2.0
/* Multipath TCP
*
* Copyright (c) 2017 - 2019, Intel Corporation.
*/
#include <linux/kernel.h>
#include <net/tcp.h>
#include <net/mptcp.h>
#include "protocol.h"
void mptcp_parse_option(const unsigned char *ptr, int opsize,
struct tcp_options_received *opt_rx)
{
struct mptcp_options_received *mp_opt = &opt_rx->mptcp;
u8 subtype = *ptr >> 4;
u8 version;
u8 flags;
switch (subtype) {
case MPTCPOPT_MP_CAPABLE:
if (opsize != TCPOLEN_MPTCP_MPC_SYN &&
opsize != TCPOLEN_MPTCP_MPC_ACK)
break;
version = *ptr++ & MPTCP_VERSION_MASK;
if (version != MPTCP_SUPPORTED_VERSION)
break;
flags = *ptr++;
if (!((flags & MPTCP_CAP_FLAG_MASK) == MPTCP_CAP_HMAC_SHA1) ||
(flags & MPTCP_CAP_EXTENSIBILITY))
break;
/* RFC 6824, Section 3.1:
* "For the Checksum Required bit (labeled "A"), if either
* host requires the use of checksums, checksums MUST be used.
* In other words, the only way for checksums not to be used
* is if both hosts in their SYNs set A=0."
*
* Section 3.3.0:
* "If a checksum is not present when its use has been
* negotiated, the receiver MUST close the subflow with a RST as
* it is considered broken."
*
* We don't implement DSS checksum - fall back to TCP.
*/
if (flags & MPTCP_CAP_CHECKSUM_REQD)
break;
mp_opt->mp_capable = 1;
mp_opt->sndr_key = get_unaligned_be64(ptr);
ptr += 8;
if (opsize == TCPOLEN_MPTCP_MPC_ACK) {
mp_opt->rcvr_key = get_unaligned_be64(ptr);
ptr += 8;
pr_debug("MP_CAPABLE sndr=%llu, rcvr=%llu",
mp_opt->sndr_key, mp_opt->rcvr_key);
} else {
pr_debug("MP_CAPABLE sndr=%llu", mp_opt->sndr_key);
}
break;
case MPTCPOPT_DSS:
pr_debug("DSS");
mp_opt->dss = 1;
break;
default:
break;
}
}
void mptcp_write_options(__be32 *ptr, struct mptcp_out_options *opts)
{
if ((OPTION_MPTCP_MPC_SYN |
OPTION_MPTCP_MPC_ACK) & opts->suboptions) {
u8 len;
if (OPTION_MPTCP_MPC_SYN & opts->suboptions)
len = TCPOLEN_MPTCP_MPC_SYN;
else
len = TCPOLEN_MPTCP_MPC_ACK;
*ptr++ = htonl((TCPOPT_MPTCP << 24) | (len << 16) |
(MPTCPOPT_MP_CAPABLE << 12) |
(MPTCP_SUPPORTED_VERSION << 8) |
MPTCP_CAP_HMAC_SHA1);
put_unaligned_be64(opts->sndr_key, ptr);
ptr += 2;
if (OPTION_MPTCP_MPC_ACK & opts->suboptions) {
put_unaligned_be64(opts->rcvr_key, ptr);
ptr += 2;
}
}
}
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