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linux/net/mptcp/options.c
Paolo Abeni d87903b63e mptcp: fix DATA_FIN generation on early shutdown 
If the msk is closed before sending or receiving any data,
no DATA_FIN is generated, instead an MPC ack packet is
crafted out.

In the above scenario, the MPTCP protocol creates and sends a
pure ack and such packets matches also the criteria for an
MPC ack and the protocol tries first to insert MPC options,
leading to the described error.

This change addresses the issue by avoiding the insertion of an
MPC option for DATA_FIN packets or if the sub-flow is not
established.

To avoid doing multiple times the same test, fetch the data_fin
flag in a bool variable and pass it to both the interested
helpers.

Fixes: 6d0060f600 ("mptcp: Write MPTCP DSS headers to outgoing data packets")
Reviewed-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
2021-02-22 18:54:59 -08:00

1315 lines
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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/sha2.h>
#include <net/tcp.h>
#include <net/mptcp.h>
#include "protocol.h"
#include "mib.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->addr_id = *ptr++;
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;
}
pr_debug("ADD_ADDR%s: id=%d, ahmac=%llu, echo=%d, port=%d",
(mp_opt->family == MPTCP_ADDR_IPVERSION_6) ? "6" : "",
mp_opt->addr_id, mp_opt->ahmac, mp_opt->echo, mp_opt->port);
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;
case MPTCPOPT_MP_PRIO:
if (opsize != TCPOLEN_MPTCP_PRIO)
break;
mp_opt->mp_prio = 1;
mp_opt->backup = *ptr++ & MPTCP_PRIO_BKUP;
pr_debug("MP_PRIO: prio=%d", mp_opt->backup);
break;
case MPTCPOPT_MP_FASTCLOSE:
if (opsize != TCPOLEN_MPTCP_FASTCLOSE)
break;
ptr += 2;
mp_opt->rcvr_key = get_unaligned_be64(ptr);
ptr += 8;
mp_opt->fastclose = 1;
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->ahmac = 0;
mp_opt->fastclose = 0;
mp_opt->port = 0;
mp_opt->rm_addr = 0;
mp_opt->dss = 0;
mp_opt->mp_prio = 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,
bool snd_data_fin_enable,
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, DATA_FIN and TCP shutdown take precedence */
if (subflow->fully_established || snd_data_fin_enable ||
subflow->snd_isn != TCP_SKB_CB(skb)->seq ||
sk->sk_state != TCP_ESTABLISHED)
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)
{
/* The write_seq value has already been incremented, so the actual
* sequence number for the DATA_FIN is one less.
*/
u64 data_fin_tx_seq = READ_ONCE(mptcp_sk(subflow->conn)->write_seq) - 1;
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;
ext->data_seq = data_fin_tx_seq;
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,
bool snd_data_fin_enable,
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;
struct mptcp_ext *mpext;
unsigned int ack_size;
bool ret = false;
u64 ack_seq;
mpext = skb ? mptcp_get_ext(skb) : NULL;
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;
}
ack_seq = READ_ONCE(msk->ack_seq);
if (READ_ONCE(msk->use_64bit_ack)) {
ack_size = TCPOLEN_MPTCP_DSS_ACK64;
opts->ext_copy.data_ack = ack_seq;
opts->ext_copy.ack64 = 1;
} else {
ack_size = TCPOLEN_MPTCP_DSS_ACK32;
opts->ext_copy.data_ack32 = (uint32_t)ack_seq;
opts->ext_copy.ack64 = 0;
}
opts->ext_copy.use_ack = 1;
WRITE_ONCE(msk->old_wspace, __mptcp_space((struct sock *)msk));
/* 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_add_addr(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);
bool drop_other_suboptions = false;
unsigned int opt_size = *size;
struct mptcp_addr_info saddr;
bool echo;
bool port;
int len;
if ((mptcp_pm_should_add_signal_ipv6(msk) ||
mptcp_pm_should_add_signal_port(msk)) &&
skb && skb_is_tcp_pure_ack(skb)) {
pr_debug("drop other suboptions");
opts->suboptions = 0;
opts->ext_copy.use_ack = 0;
opts->ext_copy.use_map = 0;
remaining += opt_size;
drop_other_suboptions = true;
}
if (!mptcp_pm_should_add_signal(msk) ||
!(mptcp_pm_add_addr_signal(msk, remaining, &saddr, &echo, &port)))
return false;
len = mptcp_add_addr_len(saddr.family, echo, port);
if (remaining < len)
return false;
*size = len;
if (drop_other_suboptions)
*size -= opt_size;
opts->addr_id = saddr.id;
if (port)
opts->port = ntohs(saddr.port);
if (saddr.family == AF_INET) {
opts->suboptions |= OPTION_MPTCP_ADD_ADDR;
opts->addr = saddr.addr;
if (!echo) {
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;
if (!echo) {
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, echo=%d, port=%d",
opts->addr_id, opts->ahmac, echo, opts->port);
return true;
}
static bool mptcp_established_options_rm_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);
u8 rm_id;
if (!mptcp_pm_should_rm_signal(msk) ||
!(mptcp_pm_rm_addr_signal(msk, remaining, &rm_id)))
return false;
if (remaining < TCPOLEN_MPTCP_RM_ADDR_BASE)
return false;
*size = TCPOLEN_MPTCP_RM_ADDR_BASE;
opts->suboptions |= OPTION_MPTCP_RM_ADDR;
opts->rm_id = rm_id;
pr_debug("rm_id=%d", opts->rm_id);
return true;
}
static bool mptcp_established_options_mp_prio(struct sock *sk,
unsigned int *size,
unsigned int remaining,
struct mptcp_out_options *opts)
{
struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
if (!subflow->send_mp_prio)
return false;
/* account for the trailing 'nop' option */
if (remaining < TCPOLEN_MPTCP_PRIO_ALIGN)
return false;
*size = TCPOLEN_MPTCP_PRIO_ALIGN;
opts->suboptions |= OPTION_MPTCP_PRIO;
opts->backup = subflow->request_bkup;
pr_debug("prio=%d", opts->backup);
return true;
}
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);
struct mptcp_sock *msk = mptcp_sk(subflow->conn);
unsigned int opt_size = 0;
bool snd_data_fin;
bool ret = false;
opts->suboptions = 0;
if (unlikely(__mptcp_check_fallback(msk)))
return false;
/* prevent adding of any MPTCP related options on reset packet
* until we support MP_TCPRST/MP_FASTCLOSE
*/
if (unlikely(skb && TCP_SKB_CB(skb)->tcp_flags & TCPHDR_RST))
return false;
snd_data_fin = mptcp_data_fin_enabled(msk);
if (mptcp_established_options_mp(sk, skb, snd_data_fin, &opt_size, remaining, opts))
ret = true;
else if (mptcp_established_options_dss(sk, skb, snd_data_fin, &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_add_addr(sk, skb, &opt_size, remaining, opts)) {
*size += opt_size;
remaining -= opt_size;
ret = true;
} else if (mptcp_established_options_rm_addr(sk, &opt_size, remaining, opts)) {
*size += opt_size;
remaining -= opt_size;
ret = true;
}
if (mptcp_established_options_mp_prio(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 *ssk,
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(ssk);
goto fully_established;
}
/* we must process OoO packets before the first subflow is fully
* established. OoO packets are instead a protocol violation
* for MP_JOIN subflows as the peer must not send any data
* before receiving the forth ack - cfr. RFC 8684 section 3.2.
*/
if (TCP_SKB_CB(skb)->seq != subflow->ssn_offset + 1) {
if (subflow->mp_join)
goto reset;
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 (mp_opt->add_addr) {
WRITE_ONCE(msk->fully_established, true);
return true;
}
/* If the first established packet does not contain MP_CAPABLE + data
* then fallback to TCP. Fallback scenarios requires a reset for
* MP_JOIN subflows.
*/
if (!mp_opt->mp_capable) {
if (subflow->mp_join)
goto reset;
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 the subflow is not already linked into the conn_list, we can't
* notify the PM: this subflow is still on the listener queue
* and the PM possibly acquiring the subflow lock could race with
* the listener close
*/
if (likely(subflow->pm_notified) || list_empty(&subflow->node))
return true;
subflow->pm_notified = 1;
if (subflow->mp_join) {
clear_3rdack_retransmission(ssk);
mptcp_pm_subflow_established(msk, subflow);
} else {
mptcp_pm_fully_established(msk, ssk, GFP_ATOMIC);
}
return true;
reset:
mptcp_subflow_reset(ssk);
return false;
}
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 ack_update_msk(struct mptcp_sock *msk,
struct sock *ssk,
struct mptcp_options_received *mp_opt)
{
u64 new_wnd_end, new_snd_una, snd_nxt = READ_ONCE(msk->snd_nxt);
struct sock *sk = (struct sock *)msk;
u64 old_snd_una;
mptcp_data_lock(sk);
/* 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
*/
old_snd_una = msk->snd_una;
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, snd_nxt))
new_snd_una = old_snd_una;
new_wnd_end = new_snd_una + tcp_sk(ssk)->snd_wnd;
if (after64(new_wnd_end, msk->wnd_end))
msk->wnd_end = new_wnd_end;
/* this assumes mptcp_incoming_options() is invoked after tcp_ack() */
if (after64(msk->wnd_end, READ_ONCE(msk->snd_nxt)))
__mptcp_check_push(sk, ssk);
if (after64(new_snd_una, old_snd_una)) {
msk->snd_una = new_snd_una;
__mptcp_data_acked(sk);
}
mptcp_data_unlock(sk);
}
bool mptcp_update_rcv_data_fin(struct mptcp_sock *msk, u64 data_fin_seq, bool use_64bit)
{
/* 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,
expand_ack(READ_ONCE(msk->ack_seq), data_fin_seq, use_64bit));
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 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)) {
/* Keep it simple and unconditionally trigger send data cleanup and
* pending queue spooling. We will need to acquire the data lock
* for more accurate checks, and once the lock is acquired, such
* helpers are cheap.
*/
mptcp_data_lock(subflow->conn);
if (sk_stream_memory_free(sk))
__mptcp_check_push(subflow->conn, sk);
__mptcp_data_acked(subflow->conn);
mptcp_data_unlock(subflow->conn);
return;
}
mptcp_get_options(skb, &mp_opt);
if (!check_fully_established(msk, sk, subflow, skb, &mp_opt))
return;
if (mp_opt.fastclose &&
msk->local_key == mp_opt.rcvr_key) {
WRITE_ONCE(msk->rcv_fastclose, true);
mptcp_schedule_work((struct sock *)msk);
}
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);
MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_ADDADDR);
} else {
mptcp_pm_del_add_timer(msk, &addr);
MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_ECHOADD);
}
if (mp_opt.port)
MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_PORTADD);
mp_opt.add_addr = 0;
}
if (mp_opt.rm_addr) {
mptcp_pm_rm_addr_received(msk, mp_opt.rm_id);
mp_opt.rm_addr = 0;
}
if (mp_opt.mp_prio) {
mptcp_pm_mp_prio_received(sk, mp_opt.backup);
MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPPRIORX);
mp_opt.mp_prio = 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)
ack_update_msk(msk, sk, &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, mp_opt.dsn64) &&
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;
}
}
static void mptcp_set_rwin(const struct tcp_sock *tp)
{
const struct sock *ssk = (const struct sock *)tp;
const struct mptcp_subflow_context *subflow;
struct mptcp_sock *msk;
u64 ack_seq;
subflow = mptcp_subflow_ctx(ssk);
msk = mptcp_sk(subflow->conn);
ack_seq = READ_ONCE(msk->ack_seq) + tp->rcv_wnd;
if (after64(ack_seq, READ_ONCE(msk->rcv_wnd_sent)))
WRITE_ONCE(msk->rcv_wnd_sent, ack_seq);
}
void mptcp_write_options(__be32 *ptr, const struct tcp_sock *tp,
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
#if IS_ENABLED(CONFIG_MPTCP_IPV6)
| OPTION_MPTCP_ADD_ADDR6
#endif
) & opts->suboptions) {
u8 len = TCPOLEN_MPTCP_ADD_ADDR_BASE;
u8 echo = MPTCP_ADDR_ECHO;
#if IS_ENABLED(CONFIG_MPTCP_IPV6)
if (OPTION_MPTCP_ADD_ADDR6 & opts->suboptions)
len = TCPOLEN_MPTCP_ADD_ADDR6_BASE;
#endif
if (opts->port)
len += TCPOLEN_MPTCP_PORT_LEN;
if (opts->ahmac) {
len += sizeof(opts->ahmac);
echo = 0;
}
*ptr++ = mptcp_option(MPTCPOPT_ADD_ADDR,
len, echo, opts->addr_id);
if (OPTION_MPTCP_ADD_ADDR & opts->suboptions) {
memcpy((u8 *)ptr, (u8 *)&opts->addr.s_addr, 4);
ptr += 1;
}
#if IS_ENABLED(CONFIG_MPTCP_IPV6)
else if (OPTION_MPTCP_ADD_ADDR6 & opts->suboptions) {
memcpy((u8 *)ptr, opts->addr6.s6_addr, 16);
ptr += 4;
}
#endif
if (!opts->port) {
if (opts->ahmac) {
put_unaligned_be64(opts->ahmac, ptr);
ptr += 2;
}
} else {
if (opts->ahmac) {
u8 *bptr = (u8 *)ptr;
put_unaligned_be16(opts->port, bptr);
bptr += 2;
put_unaligned_be64(opts->ahmac, bptr);
bptr += 8;
put_unaligned_be16(TCPOPT_NOP << 8 |
TCPOPT_NOP, bptr);
ptr += 3;
} else {
put_unaligned_be32(opts->port << 16 |
TCPOPT_NOP << 8 |
TCPOPT_NOP, ptr);
ptr += 1;
}
}
}
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_PRIO & opts->suboptions) {
const struct sock *ssk = (const struct sock *)tp;
struct mptcp_subflow_context *subflow;
subflow = mptcp_subflow_ctx(ssk);
subflow->send_mp_prio = 0;
*ptr++ = mptcp_option(MPTCPOPT_MP_PRIO,
TCPOLEN_MPTCP_PRIO,
opts->backup, TCPOPT_NOP);
}
if (OPTION_MPTCP_MPJ_SYN & opts->suboptions) {
*ptr++ = mptcp_option(MPTCPOPT_MP_JOIN,
TCPOLEN_MPTCP_MPJ_SYN,
opts->backup, opts->join_id);
put_unaligned_be32(opts->token, ptr);
ptr += 1;
put_unaligned_be32(opts->nonce, ptr);
ptr += 1;
}
if (OPTION_MPTCP_MPJ_SYNACK & opts->suboptions) {
*ptr++ = mptcp_option(MPTCPOPT_MP_JOIN,
TCPOLEN_MPTCP_MPJ_SYNACK,
opts->backup, opts->join_id);
put_unaligned_be64(opts->thmac, ptr);
ptr += 2;
put_unaligned_be32(opts->nonce, ptr);
ptr += 1;
}
if (OPTION_MPTCP_MPJ_ACK & opts->suboptions) {
*ptr++ = mptcp_option(MPTCPOPT_MP_JOIN,
TCPOLEN_MPTCP_MPJ_ACK, 0, 0);
memcpy(ptr, opts->hmac, MPTCPOPT_HMAC_LEN);
ptr += 5;
}
if (opts->ext_copy.use_ack || opts->ext_copy.use_map) {
struct mptcp_ext *mpext = &opts->ext_copy;
u8 len = TCPOLEN_MPTCP_DSS_BASE;
u8 flags = 0;
if (mpext->use_ack) {
flags = MPTCP_DSS_HAS_ACK;
if (mpext->ack64) {
len += TCPOLEN_MPTCP_DSS_ACK64;
flags |= MPTCP_DSS_ACK64;
} else {
len += TCPOLEN_MPTCP_DSS_ACK32;
}
}
if (mpext->use_map) {
len += TCPOLEN_MPTCP_DSS_MAP64;
/* Use only 64-bit mapping flags for now, add
* support for optional 32-bit mappings later.
*/
flags |= MPTCP_DSS_HAS_MAP | MPTCP_DSS_DSN64;
if (mpext->data_fin)
flags |= MPTCP_DSS_DATA_FIN;
}
*ptr++ = mptcp_option(MPTCPOPT_DSS, len, 0, flags);
if (mpext->use_ack) {
if (mpext->ack64) {
put_unaligned_be64(mpext->data_ack, ptr);
ptr += 2;
} else {
put_unaligned_be32(mpext->data_ack32, ptr);
ptr += 1;
}
}
if (mpext->use_map) {
put_unaligned_be64(mpext->data_seq, ptr);
ptr += 2;
put_unaligned_be32(mpext->subflow_seq, ptr);
ptr += 1;
put_unaligned_be32(mpext->data_len << 16 |
TCPOPT_NOP << 8 | TCPOPT_NOP, ptr);
}
}
if (tp)
mptcp_set_rwin(tp);
}
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