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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_get_options(const struct sk_buff *skb,
struct tcp_options_received *opt_rx)
{
const unsigned char *ptr;
const struct tcphdr *th = tcp_hdr(skb);
int length = (th->doff * 4) - sizeof(struct tcphdr);
ptr = (const unsigned char *)(th + 1);
while (length > 0) {
int opcode = *ptr++;
int opsize;
switch (opcode) {
case TCPOPT_EOL:
return;
case TCPOPT_NOP: /* Ref: RFC 793 section 3.1 */
length--;
continue;
default:
opsize = *ptr++;
if (opsize < 2) /* "silly options" */
return;
if (opsize > length)
return; /* don't parse partial options */
if (opcode == TCPOPT_MPTCP)
mptcp_parse_option(ptr, opsize, opt_rx);
ptr += opsize - 2;
length -= opsize;
}
}
}
bool mptcp_syn_options(struct sock *sk, unsigned int *size,
struct mptcp_out_options *opts)
{
struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
if (subflow->request_mptcp) {
pr_debug("local_key=%llu", subflow->local_key);
opts->suboptions = OPTION_MPTCP_MPC_SYN;
opts->sndr_key = subflow->local_key;
*size = TCPOLEN_MPTCP_MPC_SYN;
return true;
}
return false;
}
void mptcp_rcv_synsent(struct sock *sk)
{
struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
struct tcp_sock *tp = tcp_sk(sk);
pr_debug("subflow=%p", subflow);
if (subflow->request_mptcp && tp->rx_opt.mptcp.mp_capable) {
subflow->mp_capable = 1;
subflow->remote_key = tp->rx_opt.mptcp.sndr_key;
} else {
tcp_sk(sk)->is_mptcp = 0;
}
}
bool mptcp_established_options(struct sock *sk, struct sk_buff *skb,
unsigned int *size, unsigned int remaining,
struct mptcp_out_options *opts)
{
struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
if (subflow->mp_capable && !subflow->fourth_ack) {
opts->suboptions = OPTION_MPTCP_MPC_ACK;
opts->sndr_key = subflow->local_key;
opts->rcvr_key = subflow->remote_key;
*size = TCPOLEN_MPTCP_MPC_ACK;
subflow->fourth_ack = 1;
pr_debug("subflow=%p, local_key=%llu, remote_key=%llu",
subflow, subflow->local_key, subflow->remote_key);
return true;
}
return false;
}
bool mptcp_synack_options(const struct request_sock *req, unsigned int *size,
struct mptcp_out_options *opts)
{
struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);
if (subflow_req->mp_capable) {
opts->suboptions = OPTION_MPTCP_MPC_SYNACK;
opts->sndr_key = subflow_req->local_key;
*size = TCPOLEN_MPTCP_MPC_SYNACK;
pr_debug("subflow_req=%p, local_key=%llu",
subflow_req, subflow_req->local_key);
return true;
}
return false;
}
void mptcp_write_options(__be32 *ptr, struct mptcp_out_options *opts)
{
if ((OPTION_MPTCP_MPC_SYN |
OPTION_MPTCP_MPC_SYNACK |
OPTION_MPTCP_MPC_ACK) & opts->suboptions) {
u8 len;
if (OPTION_MPTCP_MPC_SYN & opts->suboptions)
len = TCPOLEN_MPTCP_MPC_SYN;
else if (OPTION_MPTCP_MPC_SYNACK & opts->suboptions)
len = TCPOLEN_MPTCP_MPC_SYNACK;
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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