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mptcp: add mptcp reset option support

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The MPTCP reset option allows to carry a mptcp-specific error code that
provides more information on the nature of a connection reset.

Reset option data received gets stored in the subflow context so it can
be sent to userspace via the 'subflow closed' netlink event.

When a subflow is closed, the desired error code that should be sent to
the peer is also placed in the subflow context structure.

If a reset is sent before subflow establishment could complete, e.g. on
HMAC failure during an MP_JOIN operation, the mptcp skb extension is
used to store the reset information.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Florian Westphal 2021-04-01 16:19:44 -07:00 committed by David S. Miller
parent 781bf13d4f
commit dc87efdb1a
9 changed files with 180 additions and 19 deletions
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18
include/net/mptcp.h
View File

@ -30,8 +30,8 @@ struct mptcp_ext {
ack64:1,
mpc_map:1,
frozen:1,
__unused:1;
/* one byte hole */
reset_transient:1;
u8 reset_reason:4;
};
#define MPTCP_RM_IDS_MAX 8
@ -58,6 +58,8 @@ struct mptcp_out_options {
struct mptcp_rm_list rm_list;
u8 join_id;
u8 backup;
u8 reset_reason:4;
u8 reset_transient:1;
u32 nonce;
u64 thmac;
u32 token;
@ -156,6 +158,16 @@ void mptcp_seq_show(struct seq_file *seq);
int mptcp_subflow_init_cookie_req(struct request_sock *req,
const struct sock *sk_listener,
struct sk_buff *skb);
__be32 mptcp_get_reset_option(const struct sk_buff *skb);
static inline __be32 mptcp_reset_option(const struct sk_buff *skb)
{
if (skb_ext_exist(skb, SKB_EXT_MPTCP))
return mptcp_get_reset_option(skb);
return htonl(0u);
}
#else
static inline void mptcp_init(void)
@ -236,6 +248,8 @@ static inline int mptcp_subflow_init_cookie_req(struct request_sock *req,
{
return 0; /* TCP fallback */
}
static inline __be32 mptcp_reset_option(const struct sk_buff *skb) { return htonl(0u); }
#endif /* CONFIG_MPTCP */
#if IS_ENABLED(CONFIG_MPTCP_IPV6)

11
include/uapi/linux/mptcp.h
View File

@ -174,10 +174,21 @@ enum mptcp_event_attr {
MPTCP_ATTR_FLAGS, /* u16 */
MPTCP_ATTR_TIMEOUT, /* u32 */
MPTCP_ATTR_IF_IDX, /* s32 */
MPTCP_ATTR_RESET_REASON,/* u32 */
MPTCP_ATTR_RESET_FLAGS, /* u32 */
__MPTCP_ATTR_AFTER_LAST
};
#define MPTCP_ATTR_MAX (__MPTCP_ATTR_AFTER_LAST - 1)
/* MPTCP Reset reason codes, rfc8684 */
#define MPTCP_RST_EUNSPEC 0
#define MPTCP_RST_EMPTCP 1
#define MPTCP_RST_ERESOURCE 2
#define MPTCP_RST_EPROHIBIT 3
#define MPTCP_RST_EWQ2BIG 4
#define MPTCP_RST_EBADPERF 5
#define MPTCP_RST_EMIDDLEBOX 6
#endif /* _UAPI_MPTCP_H */

21
net/ipv4/tcp_ipv4.c
View File

@ -655,14 +655,18 @@ EXPORT_SYMBOL(tcp_v4_send_check);
* Exception: precedence violation. We do not implement it in any case.
*/
#ifdef CONFIG_TCP_MD5SIG
#define OPTION_BYTES TCPOLEN_MD5SIG_ALIGNED
#else
#define OPTION_BYTES sizeof(__be32)
#endif
static void tcp_v4_send_reset(const struct sock *sk, struct sk_buff *skb)
{
const struct tcphdr *th = tcp_hdr(skb);
struct {
struct tcphdr th;
#ifdef CONFIG_TCP_MD5SIG
__be32 opt[(TCPOLEN_MD5SIG_ALIGNED >> 2)];
#endif
__be32 opt[OPTION_BYTES / sizeof(__be32)];
} rep;
struct ip_reply_arg arg;
#ifdef CONFIG_TCP_MD5SIG
@ -770,6 +774,17 @@ static void tcp_v4_send_reset(const struct sock *sk, struct sk_buff *skb)
ip_hdr(skb)->daddr, &rep.th);
}
#endif
/* Can't co-exist with TCPMD5, hence check rep.opt[0] */
if (rep.opt[0] == 0) {
__be32 mrst = mptcp_reset_option(skb);
if (mrst) {
rep.opt[0] = mrst;
arg.iov[0].iov_len += sizeof(mrst);
rep.th.doff = arg.iov[0].iov_len / 4;
}
}
arg.csum = csum_tcpudp_nofold(ip_hdr(skb)->daddr,
ip_hdr(skb)->saddr, /* XXX */
arg.iov[0].iov_len, IPPROTO_TCP, 0);

14
net/ipv6/tcp_ipv6.c
View File

@ -879,8 +879,8 @@ static void tcp_v6_send_response(const struct sock *sk, struct sk_buff *skb, u32
struct net *net = sk ? sock_net(sk) : dev_net(skb_dst(skb)->dev);
struct sock *ctl_sk = net->ipv6.tcp_sk;
unsigned int tot_len = sizeof(struct tcphdr);
__be32 mrst = 0, *topt;
struct dst_entry *dst;
__be32 *topt;
__u32 mark = 0;
if (tsecr)
@ -890,6 +890,15 @@ static void tcp_v6_send_response(const struct sock *sk, struct sk_buff *skb, u32
tot_len += TCPOLEN_MD5SIG_ALIGNED;
#endif
#ifdef CONFIG_MPTCP
if (rst && !key) {
mrst = mptcp_reset_option(skb);
if (mrst)
tot_len += sizeof(__be32);
}
#endif
buff = alloc_skb(MAX_HEADER + sizeof(struct ipv6hdr) + tot_len,
GFP_ATOMIC);
if (!buff)
@ -920,6 +929,9 @@ static void tcp_v6_send_response(const struct sock *sk, struct sk_buff *skb, u32
*topt++ = htonl(tsecr);
}
if (mrst)
*topt++ = mrst;
#ifdef CONFIG_TCP_MD5SIG
if (key) {
*topt++ = htonl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16) |

67
net/mptcp/options.c
View File

@ -305,6 +305,18 @@ static void mptcp_parse_option(const struct sk_buff *skb,
mp_opt->fastclose = 1;
break;
case MPTCPOPT_RST:
if (opsize != TCPOLEN_MPTCP_RST)
break;
if (!(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_RST))
break;
mp_opt->reset = 1;
flags = *ptr++;
mp_opt->reset_transient = flags & MPTCP_RST_TRANSIENT;
mp_opt->reset_reason = *ptr;
break;
default:
break;
}
@ -327,6 +339,7 @@ void mptcp_get_options(const struct sk_buff *skb,
mp_opt->rm_addr = 0;
mp_opt->dss = 0;
mp_opt->mp_prio = 0;
mp_opt->reset = 0;
length = (th->doff * 4) - sizeof(struct tcphdr);
ptr = (const unsigned char *)(th + 1);
@ -726,6 +739,22 @@ static bool mptcp_established_options_mp_prio(struct sock *sk,
return true;
}
static noinline void mptcp_established_options_rst(struct sock *sk, struct sk_buff *skb,
unsigned int *size,
unsigned int remaining,
struct mptcp_out_options *opts)
{
const struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
if (remaining < TCPOLEN_MPTCP_RST)
return;
*size = TCPOLEN_MPTCP_RST;
opts->suboptions |= OPTION_MPTCP_RST;
opts->reset_transient = subflow->reset_transient;
opts->reset_reason = subflow->reset_reason;
}
bool mptcp_established_options(struct sock *sk, struct sk_buff *skb,
unsigned int *size, unsigned int remaining,
struct mptcp_out_options *opts)
@ -741,11 +770,10 @@ bool mptcp_established_options(struct sock *sk, struct sk_buff *skb,
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;
if (unlikely(skb && TCP_SKB_CB(skb)->tcp_flags & TCPHDR_RST)) {
mptcp_established_options_rst(sk, skb, size, remaining, opts);
return true;
}
snd_data_fin = mptcp_data_fin_enabled(msk);
if (mptcp_established_options_mp(sk, skb, snd_data_fin, &opt_size, remaining, opts))
@ -1062,6 +1090,12 @@ void mptcp_incoming_options(struct sock *sk, struct sk_buff *skb)
mp_opt.mp_prio = 0;
}
if (mp_opt.reset) {
subflow->reset_seen = 1;
subflow->reset_reason = mp_opt.reset_reason;
subflow->reset_transient = mp_opt.reset_transient;
}
if (!mp_opt.dss)
return;
@ -1289,6 +1323,12 @@ mp_capable_done:
ptr += 5;
}
if (OPTION_MPTCP_RST & opts->suboptions)
*ptr++ = mptcp_option(MPTCPOPT_RST,
TCPOLEN_MPTCP_RST,
opts->reset_transient,
opts->reset_reason);
if (opts->ext_copy.use_ack || opts->ext_copy.use_map) {
struct mptcp_ext *mpext = &opts->ext_copy;
u8 len = TCPOLEN_MPTCP_DSS_BASE;
@ -1340,3 +1380,20 @@ mp_capable_done:
if (tp)
mptcp_set_rwin(tp);
}
__be32 mptcp_get_reset_option(const struct sk_buff *skb)
{
const struct mptcp_ext *ext = mptcp_get_ext(skb);
u8 flags, reason;
if (ext) {
flags = ext->reset_transient;
reason = ext->reset_reason;
return mptcp_option(MPTCPOPT_RST, TCPOLEN_MPTCP_RST,
flags, reason);
}
return htonl(0u);
}
EXPORT_SYMBOL_GPL(mptcp_get_reset_option);

12
net/mptcp/pm_netlink.c
View File

@ -1687,9 +1687,21 @@ static int mptcp_event_sub_closed(struct sk_buff *skb,
const struct mptcp_sock *msk,
const struct sock *ssk)
{
const struct mptcp_subflow_context *sf;
if (mptcp_event_put_token_and_ssk(skb, msk, ssk))
return -EMSGSIZE;
sf = mptcp_subflow_ctx(ssk);
if (!sf->reset_seen)
return 0;
if (nla_put_u32(skb, MPTCP_ATTR_RESET_REASON, sf->reset_reason))
return -EMSGSIZE;
if (nla_put_u32(skb, MPTCP_ATTR_RESET_FLAGS, sf->reset_transient))
return -EMSGSIZE;
return 0;
}

12
net/mptcp/protocol.c
View File

@ -3090,14 +3090,18 @@ bool mptcp_finish_join(struct sock *ssk)
pr_debug("msk=%p, subflow=%p", msk, subflow);
/* mptcp socket already closing? */
if (!mptcp_is_fully_established(parent))
if (!mptcp_is_fully_established(parent)) {
subflow->reset_reason = MPTCP_RST_EMPTCP;
return false;
}
if (!msk->pm.server_side)
goto out;
if (!mptcp_pm_allow_new_subflow(msk))
if (!mptcp_pm_allow_new_subflow(msk)) {
subflow->reset_reason = MPTCP_RST_EPROHIBIT;
return false;
}
/* active connections are already on conn_list, and we can't acquire
* msk lock here.
@ -3111,8 +3115,10 @@ bool mptcp_finish_join(struct sock *ssk)
sock_hold(ssk);
}
spin_unlock_bh(&msk->join_list_lock);
if (!ret)
if (!ret) {
subflow->reset_reason = MPTCP_RST_EPROHIBIT;
return false;
}
/* attach to msk socket only after we are sure he will deal with us
* at close time

14
net/mptcp/protocol.h
View File

@ -26,6 +26,7 @@
#define OPTION_MPTCP_RM_ADDR BIT(8)
#define OPTION_MPTCP_FASTCLOSE BIT(9)
#define OPTION_MPTCP_PRIO BIT(10)
#define OPTION_MPTCP_RST BIT(11)
/* MPTCP option subtypes */
#define MPTCPOPT_MP_CAPABLE 0
@ -36,6 +37,7 @@
#define MPTCPOPT_MP_PRIO 5
#define MPTCPOPT_MP_FAIL 6
#define MPTCPOPT_MP_FASTCLOSE 7
#define MPTCPOPT_RST 8
/* MPTCP suboption lengths */
#define TCPOLEN_MPTCP_MPC_SYN 4
@ -65,6 +67,7 @@
#define TCPOLEN_MPTCP_PRIO 3
#define TCPOLEN_MPTCP_PRIO_ALIGN 4
#define TCPOLEN_MPTCP_FASTCLOSE 12
#define TCPOLEN_MPTCP_RST 4
/* MPTCP MP_JOIN flags */
#define MPTCPOPT_BACKUP BIT(0)
@ -94,6 +97,9 @@
/* MPTCP MP_PRIO flags */
#define MPTCP_PRIO_BKUP BIT(0)
/* MPTCP TCPRST flags */
#define MPTCP_RST_TRANSIENT BIT(0)
/* MPTCP socket flags */
#define MPTCP_DATA_READY 0
#define MPTCP_NOSPACE 1
@ -123,6 +129,7 @@ struct mptcp_options_received {
u16 mp_capable : 1,
mp_join : 1,
fastclose : 1,
reset : 1,
dss : 1,
add_addr : 1,
rm_addr : 1,
@ -152,6 +159,8 @@ struct mptcp_options_received {
};
u64 ahmac;
u16 port;
u8 reset_reason:4;
u8 reset_transient:1;
};
static inline __be32 mptcp_option(u8 subopt, u8 len, u8 nib, u8 field)
@ -422,6 +431,9 @@ struct mptcp_subflow_context {
u8 hmac[MPTCPOPT_HMAC_LEN];
u8 local_id;
u8 remote_id;
u8 reset_seen:1;
u8 reset_transient:1;
u8 reset_reason:4;
long delegated_status;
struct list_head delegated_node; /* link into delegated_action, protected by local BH */
@ -742,7 +754,7 @@ unsigned int mptcp_pm_get_add_addr_accept_max(struct mptcp_sock *msk);
unsigned int mptcp_pm_get_subflows_max(struct mptcp_sock *msk);
unsigned int mptcp_pm_get_local_addr_max(struct mptcp_sock *msk);
static inline struct mptcp_ext *mptcp_get_ext(struct sk_buff *skb)
static inline struct mptcp_ext *mptcp_get_ext(const struct sk_buff *skb)
{
return (struct mptcp_ext *)skb_ext_find(skb, SKB_EXT_MPTCP);
}

30
net/mptcp/subflow.c
View File

@ -115,6 +115,16 @@ static bool subflow_use_different_sport(struct mptcp_sock *msk, const struct soc
return inet_sk(sk)->inet_sport != inet_sk((struct sock *)msk)->inet_sport;
}
static void subflow_add_reset_reason(struct sk_buff *skb, u8 reason)
{
struct mptcp_ext *mpext = skb_ext_add(skb, SKB_EXT_MPTCP);
if (mpext) {
memset(mpext, 0, sizeof(*mpext));
mpext->reset_reason = reason;
}
}
/* Init mptcp request socket.
*
* Returns an error code if a JOIN has failed and a TCP reset
@ -190,8 +200,10 @@ again:
subflow_req->msk = subflow_token_join_request(req);
/* Can't fall back to TCP in this case. */
if (!subflow_req->msk)
if (!subflow_req->msk) {
subflow_add_reset_reason(skb, MPTCP_RST_EMPTCP);
return -EPERM;
}
if (subflow_use_different_sport(subflow_req->msk, sk_listener)) {
pr_debug("syn inet_sport=%d %d",
@ -400,8 +412,10 @@ static void subflow_finish_connect(struct sock *sk, const struct sk_buff *skb)
} else if (subflow->request_join) {
u8 hmac[SHA256_DIGEST_SIZE];
if (!mp_opt.mp_join)
if (!mp_opt.mp_join) {
subflow->reset_reason = MPTCP_RST_EMPTCP;
goto do_reset;
}
subflow->thmac = mp_opt.thmac;
subflow->remote_nonce = mp_opt.nonce;
@ -410,6 +424,7 @@ static void subflow_finish_connect(struct sock *sk, const struct sk_buff *skb)
if (!subflow_thmac_valid(subflow)) {
MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_JOINACKMAC);
subflow->reset_reason = MPTCP_RST_EMPTCP;
goto do_reset;
}
@ -438,6 +453,7 @@ fallback:
return;
do_reset:
subflow->reset_transient = 0;
mptcp_subflow_reset(sk);
}
@ -654,8 +670,10 @@ create_child:
* to reset the context to non MPTCP status.
*/
if (!ctx || fallback) {
if (fallback_is_fatal)
if (fallback_is_fatal) {
subflow_add_reset_reason(skb, MPTCP_RST_EMPTCP);
goto dispose_child;
}
subflow_drop_ctx(child);
goto out;
@ -690,8 +708,10 @@ create_child:
struct mptcp_sock *owner;
owner = subflow_req->msk;
if (!owner)
if (!owner) {
subflow_add_reset_reason(skb, MPTCP_RST_EPROHIBIT);
goto dispose_child;
}
/* move the msk reference ownership to the subflow */
subflow_req->msk = NULL;
@ -1056,6 +1076,8 @@ fatal:
smp_wmb();
ssk->sk_error_report(ssk);
tcp_set_state(ssk, TCP_CLOSE);
subflow->reset_transient = 0;
subflow->reset_reason = MPTCP_RST_EMPTCP;
tcp_send_active_reset(ssk, GFP_ATOMIC);
subflow->data_avail = 0;
return false;