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options.c
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// 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 <crypto/sha.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;
}
static void mptcp_parse_option(const struct sk_buff *skb,
const unsigned char *ptr, int opsize,
struct mptcp_options_received *mp_opt)
{
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 == TCPOLEN_MPTCP_MPJ_ACK) {
ptr += 2;
memcpy(mp_opt->hmac, ptr, MPTCPOPT_HMAC_LEN);
pr_debug("MP_JOIN hmac");
} else {
pr_warn("MP_JOIN bad option size");
mp_opt->mp_join = 0;
}
break;
case MPTCPOPT_DSS:
pr_debug("DSS");
ptr++;
/* we must clear 'mpc_map' be able to detect MP_CAPABLE
* map vs DSS map in mptcp_incoming_options(), and reconstruct
* map info accordingly
*/
mp_opt->mpc_map = 0;
flags = (*ptr++) & MPTCP_DSS_FLAG_MASK;
mp_opt->data_fin = (flags & MPTCP_DSS_DATA_FIN) != 0;
mp_opt->dsn64 = (flags & MPTCP_DSS_DSN64) != 0;
mp_opt->use_map = (flags & MPTCP_DSS_HAS_MAP) != 0;
mp_opt->ack64 = (flags & MPTCP_DSS_ACK64) != 0;
mp_opt->use_ack = (flags & MPTCP_DSS_HAS_ACK);
pr_debug("data_fin=%d dsn64=%d use_map=%d ack64=%d use_ack=%d",
mp_opt->data_fin, mp_opt->dsn64,
mp_opt->use_map, mp_opt->ack64,
mp_opt->use_ack);
expected_opsize = TCPOLEN_MPTCP_DSS_BASE;
if (mp_opt->use_ack) {
if (mp_opt->ack64)
expected_opsize += TCPOLEN_MPTCP_DSS_ACK64;
else
expected_opsize += TCPOLEN_MPTCP_DSS_ACK32;
}
if (mp_opt->use_map) {
if (mp_opt->dsn64)
expected_opsize += TCPOLEN_MPTCP_DSS_MAP64;
else
expected_opsize += TCPOLEN_MPTCP_DSS_MAP32;
}
/* RFC 6824, Section 3.3:
* If a checksum is present, but its use had
* not been negotiated in the MP_CAPABLE handshake,
* the checksum field MUST be ignored.
*/
if (opsize != expected_opsize &&
opsize != expected_opsize + TCPOLEN_MPTCP_DSS_CHECKSUM)
break;
mp_opt->dss = 1;
if (mp_opt->use_ack) {
if (mp_opt->ack64) {
mp_opt->data_ack = get_unaligned_be64(ptr);
ptr += 8;
} else {
mp_opt->data_ack = get_unaligned_be32(ptr);
ptr += 4;
}
pr_debug("data_ack=%llu", mp_opt->data_ack);
}
if (mp_opt->use_map) {
if (mp_opt->dsn64) {
mp_opt->data_seq = get_unaligned_be64(ptr);
ptr += 8;
} else {
mp_opt->data_seq = get_unaligned_be32(ptr);
ptr += 4;
}
mp_opt->subflow_seq = get_unaligned_be32(ptr);
ptr += 4;
mp_opt->data_len = get_unaligned_be16(ptr);
ptr += 2;
pr_debug("data_seq=%llu subflow_seq=%u data_len=%u",
mp_opt->data_seq, mp_opt->subflow_seq,
mp_opt->data_len);
}
break;
case MPTCPOPT_ADD_ADDR:
mp_opt->echo = (*ptr++) & MPTCP_ADDR_ECHO;
if (!mp_opt->echo) {
if (opsize == TCPOLEN_MPTCP_ADD_ADDR ||
opsize == TCPOLEN_MPTCP_ADD_ADDR_PORT)
mp_opt->family = MPTCP_ADDR_IPVERSION_4;
#if IS_ENABLED(CONFIG_MPTCP_IPV6)
else if (opsize == TCPOLEN_MPTCP_ADD_ADDR6 ||
opsize == TCPOLEN_MPTCP_ADD_ADDR6_PORT)
mp_opt->family = MPTCP_ADDR_IPVERSION_6;
#endif
else
break;
} else {
if (opsize == TCPOLEN_MPTCP_ADD_ADDR_BASE ||
opsize == TCPOLEN_MPTCP_ADD_ADDR_BASE_PORT)
mp_opt->family = MPTCP_ADDR_IPVERSION_4;
#if IS_ENABLED(CONFIG_MPTCP_IPV6)
else if (opsize == TCPOLEN_MPTCP_ADD_ADDR6_BASE ||
opsize == TCPOLEN_MPTCP_ADD_ADDR6_BASE_PORT)
mp_opt->family = MPTCP_ADDR_IPVERSION_6;
#endif
else
break;
}
mp_opt->add_addr = 1;
mp_opt->port = 0;
mp_opt->addr_id = *ptr++;
pr_debug("ADD_ADDR: id=%d", mp_opt->addr_id);
if (mp_opt->family == MPTCP_ADDR_IPVERSION_4) {
memcpy((u8 *)&mp_opt->addr.s_addr, (u8 *)ptr, 4);
ptr += 4;
if (opsize == TCPOLEN_MPTCP_ADD_ADDR_PORT ||
opsize == TCPOLEN_MPTCP_ADD_ADDR_BASE_PORT) {
mp_opt->port = get_unaligned_be16(ptr);
ptr += 2;
}
}
#if IS_ENABLED(CONFIG_MPTCP_IPV6)
else {
memcpy(mp_opt->addr6.s6_addr, (u8 *)ptr, 16);
ptr += 16;
if (opsize == TCPOLEN_MPTCP_ADD_ADDR6_PORT ||
opsize == TCPOLEN_MPTCP_ADD_ADDR6_BASE_PORT) {
mp_opt->port = get_unaligned_be16(ptr);
ptr += 2;
}
}
#endif
if (!mp_opt->echo) {
mp_opt->ahmac = get_unaligned_be64(ptr);
ptr += 8;
}
break;
case MPTCPOPT_RM_ADDR:
if (opsize != TCPOLEN_MPTCP_RM_ADDR_BASE)
break;
ptr++;
mp_opt->rm_addr = 1;
mp_opt->rm_id = *ptr++;
pr_debug("RM_ADDR: id=%d", mp_opt->rm_id);
break;
default:
break;
}
}
void mptcp_get_options(const struct sk_buff *skb,
struct mptcp_options_received *mp_opt)
{
const struct tcphdr *th = tcp_hdr(skb);
const unsigned char *ptr;
int length;
/* initialize option status */
mp_opt->mp_capable = 0;
mp_opt->mp_join = 0;
mp_opt->add_addr = 0;
mp_opt->rm_addr = 0;
mp_opt->dss = 0;
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(skb, ptr, opsize, mp_opt);
ptr += opsize - 2;
length -= opsize;
}
}
}
bool mptcp_syn_options(struct sock *sk, const struct sk_buff *skb,
unsigned int *size, struct mptcp_out_options *opts)
{
struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
/* we will use snd_isn to detect first pkt [re]transmission
* in mptcp_established_options_mp()
*/
subflow->snd_isn = TCP_SKB_CB(skb)->end_seq;
if (subflow->request_mptcp) {
opts->suboptions = OPTION_MPTCP_MPC_SYN;
*size = TCPOLEN_MPTCP_MPC_SYN;
return true;
} else if (subflow->request_join) {
pr_debug("remote_token=%u, nonce=%u", subflow->remote_token,
subflow->local_nonce);
opts->suboptions = OPTION_MPTCP_MPJ_SYN;
opts->join_id = subflow->local_id;
opts->token = subflow->remote_token;
opts->nonce = subflow->local_nonce;
opts->backup = subflow->request_bkup;
*size = TCPOLEN_MPTCP_MPJ_SYN;
return true;
}
return false;
}
/* MP_JOIN client subflow must wait for 4th ack before sending any data:
* TCP can't schedule delack timer before the subflow is fully established.
* MPTCP uses the delack timer to do 3rd ack retransmissions
*/
static void schedule_3rdack_retransmission(struct sock *sk)
{
struct inet_connection_sock *icsk = inet_csk(sk);
struct tcp_sock *tp = tcp_sk(sk);
unsigned long timeout;
/* reschedule with a timeout above RTT, as we must look only for drop */
if (tp->srtt_us)
timeout = tp->srtt_us << 1;
else
timeout = TCP_TIMEOUT_INIT;
WARN_ON_ONCE(icsk->icsk_ack.pending & ICSK_ACK_TIMER);
icsk->icsk_ack.pending |= ICSK_ACK_SCHED | ICSK_ACK_TIMER;
icsk->icsk_ack.timeout = timeout;
sk_reset_timer(sk, &icsk->icsk_delack_timer, timeout);
}
static void clear_3rdack_retransmission(struct sock *sk)
{
struct inet_connection_sock *icsk = inet_csk(sk);
sk_stop_timer(sk, &icsk->icsk_delack_timer);
icsk->icsk_ack.timeout = 0;
icsk->icsk_ack.ato = 0;
icsk->icsk_ack.pending &= ~(ICSK_ACK_SCHED | ICSK_ACK_TIMER);
}
static bool mptcp_established_options_mp(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);
struct mptcp_ext *mpext;
unsigned int data_len;
/* When skb is not available, we better over-estimate the emitted
* options len. A full DSS option (28 bytes) is longer than
* TCPOLEN_MPTCP_MPC_ACK_DATA(22) or TCPOLEN_MPTCP_MPJ_ACK(24), so
* tell the caller to defer the estimate to
* mptcp_established_options_dss(), which will reserve enough space.
*/
if (!skb)
return false;
/* MPC/MPJ needed only on 3rd ack packet */
if (subflow->fully_established ||
subflow->snd_isn != TCP_SKB_CB(skb)->seq)
return false;
if (subflow->mp_capable) {
mpext = mptcp_get_ext(skb);
data_len = mpext ? mpext->data_len : 0;
/* we will check ext_copy.data_len in mptcp_write_options() to
* discriminate between TCPOLEN_MPTCP_MPC_ACK_DATA and
* TCPOLEN_MPTCP_MPC_ACK
*/
opts->ext_copy.data_len = data_len;
opts->suboptions = OPTION_MPTCP_MPC_ACK;
opts->sndr_key = subflow->local_key;
opts->rcvr_key = subflow->remote_key;
/* Section 3.1.
* The MP_CAPABLE option is carried on the SYN, SYN/ACK, and ACK
* packets that start the first subflow of an MPTCP connection,
* as well as the first packet that carries data
*/
if (data_len > 0)
*size = ALIGN(TCPOLEN_MPTCP_MPC_ACK_DATA, 4);
else
*size = TCPOLEN_MPTCP_MPC_ACK;
pr_debug("subflow=%p, local_key=%llu, remote_key=%llu map_len=%d",
subflow, subflow->local_key, subflow->remote_key,
data_len);
return true;
} else if (subflow->mp_join) {
opts->suboptions = OPTION_MPTCP_MPJ_ACK;
memcpy(opts->hmac, subflow->hmac, MPTCPOPT_HMAC_LEN);
*size = TCPOLEN_MPTCP_MPJ_ACK;
pr_debug("subflow=%p", subflow);
schedule_3rdack_retransmission(sk);
return true;
}
return false;
}
static void mptcp_write_data_fin(struct mptcp_subflow_context *subflow,
struct sk_buff *skb, struct mptcp_ext *ext)
{
u64 data_fin_tx_seq = READ_ONCE(mptcp_sk(subflow->conn)->write_seq);
if (!ext->use_map || !skb->len) {
/* RFC6824 requires a DSS mapping with specific values
* if DATA_FIN is set but no data payload is mapped
*/
ext->data_fin = 1;
ext->use_map = 1;
ext->dsn64 = 1;
/* The write_seq value has already been incremented, so
* the actual sequence number for the DATA_FIN is one less.
*/
ext->data_seq = data_fin_tx_seq - 1;
ext->subflow_seq = 0;
ext->data_len = 1;
} else if (ext->data_seq + ext->data_len == data_fin_tx_seq) {
/* If there's an existing DSS mapping and it is the
* final mapping, DATA_FIN consumes 1 additional byte of
* mapping space.
*/
ext->data_fin = 1;
ext->data_len++;
}
}
static bool mptcp_established_options_dss(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);
struct mptcp_sock *msk = mptcp_sk(subflow->conn);
unsigned int dss_size = 0;
u64 snd_data_fin_enable;
struct mptcp_ext *mpext;
unsigned int ack_size;
bool ret = false;
mpext = skb ? mptcp_get_ext(skb) : NULL;
snd_data_fin_enable = READ_ONCE(msk->snd_data_fin_enable);
if (!skb || (mpext && mpext->use_map) || snd_data_fin_enable) {
unsigned int map_size;
map_size = TCPOLEN_MPTCP_DSS_BASE + TCPOLEN_MPTCP_DSS_MAP64;
remaining -= map_size;
dss_size = map_size;
if (mpext)
opts->ext_copy = *mpext;
if (skb && snd_data_fin_enable)
mptcp_write_data_fin(subflow, skb, &opts->ext_copy);
ret = true;
}
/* passive sockets msk will set the 'can_ack' after accept(), even
* if the first subflow may have the already the remote key handy
*/
opts->ext_copy.use_ack = 0;
if (!READ_ONCE(msk->can_ack)) {
*size = ALIGN(dss_size, 4);
return ret;
}
if (subflow->use_64bit_ack) {
ack_size = TCPOLEN_MPTCP_DSS_ACK64;
opts->ext_copy.data_ack = msk->ack_seq;
opts->ext_copy.ack64 = 1;
} else {
ack_size = TCPOLEN_MPTCP_DSS_ACK32;
opts->ext_copy.data_ack32 = (uint32_t)(msk->ack_seq);
opts->ext_copy.ack64 = 0;
}
opts->ext_copy.use_ack = 1;
/* Add kind/length/subtype/flag overhead if mapping is not populated */
if (dss_size == 0)
ack_size += TCPOLEN_MPTCP_DSS_BASE;
dss_size += ack_size;
*size = ALIGN(dss_size, 4);
return true;
}
static u64 add_addr_generate_hmac(u64 key1, u64 key2, u8 addr_id,
struct in_addr *addr)
{
u8 hmac[SHA256_DIGEST_SIZE];
u8 msg[7];
msg[0] = addr_id;
memcpy(&msg[1], &addr->s_addr, 4);
msg[5] = 0;
msg[6] = 0;
mptcp_crypto_hmac_sha(key1, key2, msg, 7, hmac);
return get_unaligned_be64(&hmac[SHA256_DIGEST_SIZE - sizeof(u64)]);
}
#if IS_ENABLED(CONFIG_MPTCP_IPV6)
static u64 add_addr6_generate_hmac(u64 key1, u64 key2, u8 addr_id,
struct in6_addr *addr)
{
u8 hmac[SHA256_DIGEST_SIZE];
u8 msg[19];
msg[0] = addr_id;
memcpy(&msg[1], &addr->s6_addr, 16);
msg[17] = 0;
msg[18] = 0;
mptcp_crypto_hmac_sha(key1, key2, msg, 19, hmac);
return get_unaligned_be64(&hmac[SHA256_DIGEST_SIZE - sizeof(u64)]);
}
#endif
static bool mptcp_established_options_addr(struct sock *sk,
unsigned int *size,
unsigned int remaining,
struct mptcp_out_options *opts)
{
struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
struct mptcp_sock *msk = mptcp_sk(subflow->conn);
struct mptcp_addr_info saddr;
int len;
if (!mptcp_pm_should_signal(msk) ||
!(mptcp_pm_addr_signal(msk, remaining, &saddr)))
return false;
len = mptcp_add_addr_len(saddr.family);
if (remaining < len)
return false;
*size = len;
opts->addr_id = saddr.id;
if (saddr.family == AF_INET) {
opts->suboptions |= OPTION_MPTCP_ADD_ADDR;
opts->addr = saddr.addr;
opts->ahmac = add_addr_generate_hmac(msk->local_key,
msk->remote_key,
opts->addr_id,
&opts->addr);
}
#if IS_ENABLED(CONFIG_MPTCP_IPV6)
else if (saddr.family == AF_INET6) {
opts->suboptions |= OPTION_MPTCP_ADD_ADDR6;
opts->addr6 = saddr.addr6;
opts->ahmac = add_addr6_generate_hmac(msk->local_key,
msk->remote_key,
opts->addr_id,
&opts->addr6);
}
#endif
pr_debug("addr_id=%d, ahmac=%llu", opts->addr_id, opts->ahmac);
return true;
}
bool mptcp_established_options(struct sock *sk, struct sk_buff *skb,
unsigned int *size, unsigned int remaining,
struct mptcp_out_options *opts)
{
unsigned int opt_size = 0;
bool ret = false;
opts->suboptions = 0;
if (unlikely(mptcp_check_fallback(sk)))
return false;
if (mptcp_established_options_mp(sk, skb, &opt_size, remaining, opts))
ret = true;
else if (mptcp_established_options_dss(sk, skb, &opt_size, remaining,
opts))
ret = true;
/* we reserved enough space for the above options, and exceeding the
* TCP option space would be fatal
*/
if (WARN_ON_ONCE(opt_size > remaining))
return false;
*size += opt_size;
remaining -= opt_size;
if (mptcp_established_options_addr(sk, &opt_size, remaining, opts)) {
*size += opt_size;
remaining -= opt_size;
ret = true;
}
return ret;
}
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;
} else if (subflow_req->mp_join) {
opts->suboptions = OPTION_MPTCP_MPJ_SYNACK;
opts->backup = subflow_req->backup;
opts->join_id = subflow_req->local_id;
opts->thmac = subflow_req->thmac;
opts->nonce = subflow_req->local_nonce;
pr_debug("req=%p, bkup=%u, id=%u, thmac=%llu, nonce=%u",
subflow_req, opts->backup, opts->join_id,
opts->thmac, opts->nonce);
*size = TCPOLEN_MPTCP_MPJ_SYNACK;
return true;
}
return false;
}
static bool check_fully_established(struct mptcp_sock *msk, struct sock *sk,
struct mptcp_subflow_context *subflow,
struct sk_buff *skb,
struct mptcp_options_received *mp_opt)
{
/* here we can process OoO, in-window pkts, only in-sequence 4th ack
* will make the subflow fully established
*/
if (likely(subflow->fully_established)) {
/* on passive sockets, check for 3rd ack retransmission
* note that msk is always set by subflow_syn_recv_sock()
* for mp_join subflows
*/
if (TCP_SKB_CB(skb)->seq == subflow->ssn_offset + 1 &&
TCP_SKB_CB(skb)->end_seq == TCP_SKB_CB(skb)->seq &&
subflow->mp_join && mp_opt->mp_join &&
READ_ONCE(msk->pm.server_side))
tcp_send_ack(sk);
goto fully_established;
}
/* we should process OoO packets before the first subflow is fully
* established, but not expected for MP_JOIN subflows
*/
if (TCP_SKB_CB(skb)->seq != subflow->ssn_offset + 1)
return subflow->mp_capable;
if (mp_opt->dss && mp_opt->use_ack) {
/* subflows are fully established as soon as we get any
* additional ack.
*/
subflow->fully_established = 1;
WRITE_ONCE(msk->fully_established, true);
goto fully_established;
}
/* If the first established packet does not contain MP_CAPABLE + data
* then fallback to TCP
*/
if (!mp_opt->mp_capable) {
subflow->mp_capable = 0;
pr_fallback(msk);
__mptcp_do_fallback(msk);
return false;
}
if (unlikely(!READ_ONCE(msk->pm.server_side)))
pr_warn_once("bogus mpc option on established client sk");
mptcp_subflow_fully_established(subflow, mp_opt);
fully_established:
if (likely(subflow->pm_notified))
return true;
subflow->pm_notified = 1;
if (subflow->mp_join) {
clear_3rdack_retransmission(sk);
mptcp_pm_subflow_established(msk, subflow);
} else {
mptcp_pm_fully_established(msk);
}
return true;
}
static u64 expand_ack(u64 old_ack, u64 cur_ack, bool use_64bit)
{
u32 old_ack32, cur_ack32;
if (use_64bit)
return cur_ack;
old_ack32 = (u32)old_ack;
cur_ack32 = (u32)cur_ack;
cur_ack = (old_ack & GENMASK_ULL(63, 32)) + cur_ack32;
if (unlikely(before(cur_ack32, old_ack32)))
return cur_ack + (1LL << 32);
return cur_ack;
}
static void update_una(struct mptcp_sock *msk,
struct mptcp_options_received *mp_opt)
{
u64 new_snd_una, snd_una, old_snd_una = atomic64_read(&msk->snd_una);
u64 write_seq = READ_ONCE(msk->write_seq);
/* avoid ack expansion on update conflict, to reduce the risk of
* wrongly expanding to a future ack sequence number, which is way
* more dangerous than missing an ack
*/
new_snd_una = expand_ack(old_snd_una, mp_opt->data_ack, mp_opt->ack64);
/* ACK for data not even sent yet? Ignore. */
if (after64(new_snd_una, write_seq))
new_snd_una = old_snd_una;
while (after64(new_snd_una, old_snd_una)) {
snd_una = old_snd_una;
old_snd_una = atomic64_cmpxchg(&msk->snd_una, snd_una,
new_snd_una);
if (old_snd_una == snd_una) {
mptcp_data_acked((struct sock *)msk);
break;
}
}
}
bool mptcp_update_rcv_data_fin(struct mptcp_sock *msk, u64 data_fin_seq)
{
/* Skip if DATA_FIN was already received.
* If updating simultaneously with the recvmsg loop, values
* should match. If they mismatch, the peer is misbehaving and
* we will prefer the most recent information.
*/
if (READ_ONCE(msk->rcv_data_fin) || !READ_ONCE(msk->first))
return false;
WRITE_ONCE(msk->rcv_data_fin_seq, data_fin_seq);
WRITE_ONCE(msk->rcv_data_fin, 1);
return true;
}
static bool add_addr_hmac_valid(struct mptcp_sock *msk,
struct mptcp_options_received *mp_opt)
{
u64 hmac = 0;
if (mp_opt->echo)
return true;
if (mp_opt->family == MPTCP_ADDR_IPVERSION_4)
hmac = add_addr_generate_hmac(msk->remote_key,
msk->local_key,
mp_opt->addr_id, &mp_opt->addr);
#if IS_ENABLED(CONFIG_MPTCP_IPV6)
else
hmac = add_addr6_generate_hmac(msk->remote_key,
msk->local_key,
mp_opt->addr_id, &mp_opt->addr6);
#endif
pr_debug("msk=%p, ahmac=%llu, mp_opt->ahmac=%llu\n",
msk, (unsigned long long)hmac,
(unsigned long long)mp_opt->ahmac);
return hmac == mp_opt->ahmac;
}
void mptcp_incoming_options(struct sock *sk, struct sk_buff *skb,
struct tcp_options_received *opt_rx)
{
struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
struct mptcp_sock *msk = mptcp_sk(subflow->conn);
struct mptcp_options_received mp_opt;
struct mptcp_ext *mpext;
if (__mptcp_check_fallback(msk))
return;
mptcp_get_options(skb, &mp_opt);
if (!check_fully_established(msk, sk, subflow, skb, &mp_opt))
return;
if (mp_opt.add_addr && add_addr_hmac_valid(msk, &mp_opt)) {
struct mptcp_addr_info addr;
addr.port = htons(mp_opt.port);
addr.id = mp_opt.addr_id;
if (mp_opt.family == MPTCP_ADDR_IPVERSION_4) {
addr.family = AF_INET;
addr.addr = mp_opt.addr;
}
#if IS_ENABLED(CONFIG_MPTCP_IPV6)
else if (mp_opt.family == MPTCP_ADDR_IPVERSION_6) {
addr.family = AF_INET6;
addr.addr6 = mp_opt.addr6;
}
#endif
if (!mp_opt.echo)
mptcp_pm_add_addr_received(msk, &addr);
mp_opt.add_addr = 0;
}
if (!mp_opt.dss)
return;
/* we can't wait for recvmsg() to update the ack_seq, otherwise
* monodirectional flows will stuck
*/
if (mp_opt.use_ack)
update_una(msk, &mp_opt);
/* Zero-data-length packets are dropped by the caller and not
* propagated to the MPTCP layer, so the skb extension does not
* need to be allocated or populated. DATA_FIN information, if
* present, needs to be updated here before the skb is freed.
*/
if (TCP_SKB_CB(skb)->seq == TCP_SKB_CB(skb)->end_seq) {
if (mp_opt.data_fin && mp_opt.data_len == 1 &&
mptcp_update_rcv_data_fin(msk, mp_opt.data_seq) &&
schedule_work(&msk->work))
sock_hold(subflow->conn);
return;
}
mpext = skb_ext_add(skb, SKB_EXT_MPTCP);
if (!mpext)
return;
memset(mpext, 0, sizeof(*mpext));
if (mp_opt.use_map) {
if (mp_opt.mpc_map) {
/* this is an MP_CAPABLE carrying MPTCP data
* we know this map the first chunk of data
*/
mptcp_crypto_key_sha(subflow->remote_key, NULL,
&mpext->data_seq);
mpext->data_seq++;
mpext->subflow_seq = 1;
mpext->dsn64 = 1;
mpext->mpc_map = 1;
mpext->data_fin = 0;
} else {
mpext->data_seq = mp_opt.data_seq;
mpext->subflow_seq = mp_opt.subflow_seq;
mpext->dsn64 = mp_opt.dsn64;
mpext->data_fin = mp_opt.data_fin;
}
mpext->data_len = mp_opt.data_len;
mpext->use_map = 1;
}
}
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 if (opts->ext_copy.data_len)
len = TCPOLEN_MPTCP_MPC_ACK_DATA;
else
len = TCPOLEN_MPTCP_MPC_ACK;
*ptr++ = mptcp_option(MPTCPOPT_MP_CAPABLE, len,
MPTCP_SUPPORTED_VERSION,
MPTCP_CAP_HMAC_SHA256);
if (!((OPTION_MPTCP_MPC_SYNACK | OPTION_MPTCP_MPC_ACK) &
opts->suboptions))
goto mp_capable_done;
put_unaligned_be64(opts->sndr_key, ptr);
ptr += 2;
if (!((OPTION_MPTCP_MPC_ACK) & opts->suboptions))
goto mp_capable_done;
put_unaligned_be64(opts->rcvr_key, ptr);
ptr += 2;
if (!opts->ext_copy.data_len)
goto mp_capable_done;
put_unaligned_be32(opts->ext_copy.data_len << 16 |
TCPOPT_NOP << 8 | TCPOPT_NOP, ptr);
ptr += 1;
}
mp_capable_done:
if (OPTION_MPTCP_ADD_ADDR & opts->suboptions) {
if (opts->ahmac)
*ptr++ = mptcp_option(MPTCPOPT_ADD_ADDR,
TCPOLEN_MPTCP_ADD_ADDR, 0,
opts->addr_id);
else
*ptr++ = mptcp_option(MPTCPOPT_ADD_ADDR,
TCPOLEN_MPTCP_ADD_ADDR_BASE,
MPTCP_ADDR_ECHO,
opts->addr_id);
memcpy((u8 *)ptr, (u8 *)&opts->addr.s_addr, 4);
ptr += 1;
if (opts->ahmac) {
put_unaligned_be64(opts->ahmac, ptr);
ptr += 2;
}
}
#if IS_ENABLED(CONFIG_MPTCP_IPV6)
if (OPTION_MPTCP_ADD_ADDR6 & opts->suboptions) {
if (opts->ahmac)
*ptr++ = mptcp_option(MPTCPOPT_ADD_ADDR,
TCPOLEN_MPTCP_ADD_ADDR6, 0,
opts->addr_id);
else
*ptr++ = mptcp_option(MPTCPOPT_ADD_ADDR,
TCPOLEN_MPTCP_ADD_ADDR6_BASE,
MPTCP_ADDR_ECHO,
opts->addr_id);
memcpy((u8 *)ptr, opts->addr6.s6_addr, 16);
ptr += 4;
if (opts->ahmac) {
put_unaligned_be64(opts->ahmac, ptr);
ptr += 2;
}
}
#endif
if (OPTION_MPTCP_RM_ADDR & opts->suboptions) {
*ptr++ = mptcp_option(MPTCPOPT_RM_ADDR,
TCPOLEN_MPTCP_RM_ADDR_BASE,
0, opts->rm_id);
}
if (OPTION_MPTCP_MPJ_SYN & opts->suboptions) {
*ptr++ = mptcp_option(MPTCPOPT_MP_JOIN,
TCPOLEN_MPTCP_MPJ_SYN,
opts->backup, opts->join_id);