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mptcp: pm: drop TCP TS with ADD_ADDRv6 + port

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With TCP-timestamps (padded) taking 12 bytes and ADD_ADDR IPv6 + port
taking 30 bytes, the 40-byte limit for the TCP options is reached. In
this case, it is then not possible to send the signal.

To be able to send this ADD_ADDR, the TCP timestamps option can now be
dropped. This is done, when needed by setting the *drop_ts parameter
from mptcp_established_options. This feature is controlled by a new
net.mptcp.add_addr_v6_port_drop_ts sysctl knob, enabled by default.

It is important to keep in mind that dropping the TCP timestamps option
for one packet of the connection could eventually disrupt some
middleboxes: even if it should be unlikely, they could drop the packet
or even block the connection. That's why this new feature can be
controlled by a sysctl knob.

Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/448
Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Link: https://patch.msgid.link/20260605-net-next-mptcp-add-addr6-port-ts-v2-6-758e7ca73f4d@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Matthieu Baerts (NGI0) 2026-06-05 19:21:50 +10:00 committed by Jakub Kicinski
parent 1c3e7e0439
commit 23eeaad0d8
3 changed files with 21 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

9
net/mptcp/options.c
View File

@ -659,11 +659,13 @@ static u64 add_addr_generate_hmac(u64 key1, u64 key2,
static bool mptcp_established_options_add_addr(struct sock *sk,
struct sk_buff *skb, int *size,
unsigned int remaining,
bool has_ts,
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 addr;
bool drop_ts = has_ts;
bool echo;
/* add addr will strip the existing options, be sure to avoid breaking
@ -672,11 +674,13 @@ static bool mptcp_established_options_add_addr(struct sock *sk,
if (!mptcp_pm_should_add_signal(msk) ||
(opts->suboptions & (OPTION_MPTCP_MPJ_ACK | OPTION_MPTCP_MPC_ACK)) ||
!skb || !skb_is_tcp_pure_ack(skb) ||
!mptcp_pm_add_addr_signal(msk, size, remaining, &addr, &echo))
!mptcp_pm_add_addr_signal(msk, size, remaining, &addr, &echo,
&drop_ts))
return false;
pr_debug("drop other suboptions\n");
opts->suboptions = OPTION_MPTCP_ADD_ADDR;
opts->drop_ts = drop_ts;
opts->addr = addr;
if (!echo) {
MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_ADDADDRTX);
@ -859,7 +863,8 @@ int mptcp_established_options(struct sock *sk, struct sk_buff *skb,
total_size += opt_size;
remaining -= opt_size;
if (mptcp_established_options_add_addr(sk, skb, &opt_size, remaining, opts)) {
if (mptcp_established_options_add_addr(sk, skb, &opt_size, remaining,
has_ts, opts)) {
total_size += opt_size;
remaining -= opt_size;
ret = true;

13
net/mptcp/pm.c
View File

@ -903,7 +903,8 @@ static int mptcp_add_addr_len(int family, bool echo, bool port)
}
bool mptcp_pm_add_addr_signal(struct mptcp_sock *msk, int *size, int remaining,
struct mptcp_addr_info *addr, bool *echo)
struct mptcp_addr_info *addr, bool *echo,
bool *drop_ts)
{
bool skip_add_addr = false;
bool ret = false;
@ -941,6 +942,13 @@ bool mptcp_pm_add_addr_signal(struct mptcp_sock *msk, int *size, int remaining,
if (len > remaining) {
struct net *net = sock_net((struct sock *)msk);
if (*drop_ts && mptcp_add_addr_v6_port_drop_ts(net)) {
/* OK without TCP Timestamps? */
len -= TCPOLEN_TSTAMP_ALIGNED;
if (len <= remaining)
goto enough_space;
}
if (*echo) {
MPTCP_INC_STATS(net, MPTCP_MIB_ECHOADDTXDROP);
} else {
@ -950,6 +958,9 @@ bool mptcp_pm_add_addr_signal(struct mptcp_sock *msk, int *size, int remaining,
goto drop_signal_mark;
}
*drop_ts = false;
enough_space:
ret = true;
*size = len;

3
net/mptcp/protocol.h
View File

@ -1208,7 +1208,8 @@ static inline bool mptcp_pm_is_kernel(const struct mptcp_sock *msk)
}
bool mptcp_pm_add_addr_signal(struct mptcp_sock *msk, int *size, int remaining,
struct mptcp_addr_info *addr, bool *echo);
struct mptcp_addr_info *addr, bool *echo,
bool *drop_ts);
bool mptcp_pm_rm_addr_signal(struct mptcp_sock *msk, unsigned int remaining,
struct mptcp_rm_list *rm_list, int *len);
int mptcp_pm_get_local_id(struct mptcp_sock *msk, struct sock_common *skc);