// SPDX-License-Identifier: GPL-2.0
/* Multipath TCP
*
* Copyright (c) 2017 - 2019, Intel Corporation.
*/
#define pr_fmt(fmt) "MPTCP: " fmt
#include <linux/kernel.h>
#include <net/tcp.h>
#include <net/mptcp.h>
#include "protocol.h"
static bool mptcp_cap_flag_sha256(u8 flags)
{
return (flags & MPTCP_CAP_FLAG_MASK) == MPTCP_CAP_HMAC_SHA256;
}
void mptcp_parse_option(const struct sk_buff *skb, 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;
int expected_opsize;
u8 version;
u8 flags;
switch (subtype) {
case MPTCPOPT_MP_CAPABLE:
/* strict size checking */
if (!(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)) {
if (skb->len > tcp_hdr(skb)->doff << 2)
expected_opsize = TCPOLEN_MPTCP_MPC_ACK_DATA;
else
expected_opsize = TCPOLEN_MPTCP_MPC_ACK;
} else {
if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_ACK)
expected_opsize = TCPOLEN_MPTCP_MPC_SYNACK;
else
expected_opsize = TCPOLEN_MPTCP_MPC_SYN;
}
if (opsize != expected_opsize)
break;
/* try to be gentle vs future versions on the initial syn */
version = *ptr++ & MPTCP_VERSION_MASK;
if (opsize != TCPOLEN_MPTCP_MPC_SYN) {
if (version != MPTCP_SUPPORTED_VERSION)
break;
} else if (version < MPTCP_SUPPORTED_VERSION) {
break;
}
flags = *ptr++;
if (!mptcp_cap_flag_sha256(flags) ||
(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;
if (opsize >= TCPOLEN_MPTCP_MPC_SYNACK) {
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;
}
if (opsize == TCPOLEN_MPTCP_MPC_ACK_DATA) {
/* Section 3.1.:
* "the data parameters in a MP_CAPABLE are semantically
* equivalent to those in a DSS option and can be used
* interchangeably."
*/
mp_opt->dss = 1;
mp_opt->use_map = 1;
mp_opt->mpc_map = 1;
mp_opt->data_len = get_unaligned_be16(ptr);
ptr += 2;
}
pr_debug("MP_CAPABLE version=%x, flags=%x, optlen=%d sndr=%llu, rcvr=%llu len=%d",
version, flags, opsize, mp_opt->sndr_key,
mp_opt->rcvr_key, mp_opt->data_len);
break;
case MPTCPOPT_MP_JOIN:
mp_opt->mp_join = 1;
if (opsize == TCPOLEN_MPTCP_MPJ_SYN) {
mp_opt->backup = *ptr++ & MPTCPOPT_BACKUP;
mp_opt->join_id = *ptr++;
mp_opt->token = get_unaligned_be32(ptr);
ptr += 4;
mp_opt->nonce = get_unaligned_be32(ptr);
ptr += 4;
pr_debug("MP_JOIN bkup=%u, id=%u, token=%u, nonce=%u",
mp_opt->backup, mp_opt->join_id,
mp_opt->token, mp_opt->nonce);
} else if (opsize == TCPOLEN_MPTCP_MPJ_SYNACK) {
mp_opt->backup = *ptr++ & MPTCPOPT_BACKUP;
mp_opt->join_id = *ptr++;
mp_opt->thmac = get_unaligned_be64(ptr);
ptr += 8;
mp_opt->nonce = get_unaligned_be32(ptr);
ptr += 4;
pr_debug("MP_JOIN bkup=%u, id=%u, thmac=%llu, nonce=%u",
mp_opt->backup, mp_opt->join_id,
mp_opt->thmac, mp_opt->nonce);
} else if (opsize ==