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mptcp: fix fallback for MP_JOIN subflows

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Additional/MP_JOIN subflows that do not pass some initial handshake
tests currently causes fallback to TCP. That is an RFC violation:
we should instead reset the subflow and leave the the msk untouched.

Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/91
Fixes: f296234c98 ("mptcp: Add handling of incoming MP_JOIN requests")
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>
This commit is contained in:
Paolo Abeni 2020-10-09 19:00:00 +02:00 committed by Jakub Kicinski
parent 16cb365380
commit d582484726
3 changed files with 34 additions and 9 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

32
net/mptcp/options.c
View file

@ -626,6 +626,12 @@ bool mptcp_established_options(struct sock *sk, struct sk_buff *skb,
if (unlikely(mptcp_check_fallback(sk)))
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 (mptcp_established_options_mp(sk, skb, &opt_size, remaining, opts))
ret = true;
else if (mptcp_established_options_dss(sk, skb, &opt_size, remaining,
@ -676,7 +682,7 @@ bool mptcp_synack_options(const struct request_sock *req, unsigned int *size,
return false;
}
static bool check_fully_established(struct mptcp_sock *msk, struct sock *sk,
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)
@ -693,15 +699,20 @@ static bool check_fully_established(struct mptcp_sock *msk, struct sock *sk,
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);
tcp_send_ack(ssk);
goto fully_established;
}
/* we should process OoO packets before the first subflow is fully
* established, but not expected for MP_JOIN subflows
/* 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 (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
@ -713,9 +724,12 @@ static bool check_fully_established(struct mptcp_sock *msk, struct sock *sk,
}
/* If the first established packet does not contain MP_CAPABLE + data
* then fallback to TCP
* 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);
@ -732,12 +746,16 @@ static bool check_fully_established(struct mptcp_sock *msk, struct sock *sk,
subflow->pm_notified = 1;
if (subflow->mp_join) {
clear_3rdack_retransmission(sk);
clear_3rdack_retransmission(ssk);
mptcp_pm_subflow_established(msk, subflow);
} else {
mptcp_pm_fully_established(msk);
}
return true;
reset:
mptcp_subflow_reset(ssk);
return false;
}
static u64 expand_ack(u64 old_ack, u64 cur_ack, bool use_64bit)

1
net/mptcp/protocol.h
View file

@ -348,6 +348,7 @@ void mptcp_subflow_fully_established(struct mptcp_subflow_context *subflow,
struct mptcp_options_received *mp_opt);
bool mptcp_subflow_data_available(struct sock *sk);
void __init mptcp_subflow_init(void);
void mptcp_subflow_reset(struct sock *ssk);
/* called with sk socket lock held */
int __mptcp_subflow_connect(struct sock *sk, int ifindex,

10
net/mptcp/subflow.c
View file

@ -270,6 +270,13 @@ static bool subflow_thmac_valid(struct mptcp_subflow_context *subflow)
return thmac == subflow->thmac;
}
void mptcp_subflow_reset(struct sock *ssk)
{
tcp_set_state(ssk, TCP_CLOSE);
tcp_send_active_reset(ssk, GFP_ATOMIC);
tcp_done(ssk);
}
static void subflow_finish_connect(struct sock *sk, const struct sk_buff *skb)
{
struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
@ -342,8 +349,7 @@ static void subflow_finish_connect(struct sock *sk, const struct sk_buff *skb)
return;
do_reset:
tcp_send_active_reset(sk, GFP_ATOMIC);
tcp_done(sk);
mptcp_subflow_reset(sk);
}
struct request_sock_ops mptcp_subflow_request_sock_ops;