Multipath TCP (MPTCP), standardized in RFC8684 [1], is a TCP extension
that enables a TCP connection to use different paths. It allows a device
to make use of multiple interfaces at once to send and receive TCP
packets over a single MPTCP connection. MPTCP can aggregate the
bandwidth of multiple interfaces or prefer the one with the lowest
latency, it also allows a fail-over if one path is down, and the traffic
is seamlessly re-injected on other paths.
To benefit from MPTCP, both the client and the server have to support
it. Multipath TCP is a backward-compatible TCP extension that is enabled
by default on recent Linux distributions (Debian, Ubuntu, Redhat, ...).
Multipath TCP is included in the Linux kernel since version 5.6 [2]. To
use it on Linux, an application must explicitly enable it when creating
the socket:
int sd = socket(AF_INET(6), SOCK_STREAM, IPPROTO_MPTCP);
No need to change anything else in the application.
This patch allows MPTCP protocol in the Socket unit configuration. So
now, a <unit>.socket can contain this to use MPTCP instead of TCP:
[Socket]
SocketProtocol=mptcp
MPTCP support has been allowed similarly to what has been already done
to allow SCTP: just one line in core/socket.c, a very simple addition
thanks to the flexible architecture already in place.
On top of that, IPPROTO_MPTCP has also been added in the list of allowed
protocols in two other places, and in the doc. It has also been added to
the missing_network.h file, for systems with an old libc -- note that it
was also required to include <netinet/in.h> in this file to avoid
redefinition errors.
Link: https://www.rfc-editor.org/rfc/rfc8684.html [1]
Link: https://www.mptcp.dev [2]
Set the $REMOTE_ADDR environment variable for AF_UNIX socket connections
when using per-connection socket activation (Accept=yes). $REMOTE_ADDR
will now contain the remote socket's file system path (starting with a
slash "/") or its address in the abstract namespace (starting with an
at symbol "@").
This information is essential for identifying the remote peer in AF_UNIX
socket connections, but it's not easy to obtain in a shell script for
example without pulling in a ton of additional tools. By setting
$REMOTE_ADDR, we make this information readily available to the
activated service.
Since we document /usr/local/lib/systemd/ and other paths for various things,
add notes that this is not supported if /usr/local is a separate partition. In
systemd.unit, I tried to add the footnote in the table where
/usr/local/lib/systemd/ is listed, but that get's rendered as '[sup]a[/sup]'
with a mangled footnote at the bottom of the table :( .
Also, split paragraphs in one place where the subject changes without any
transition.
Follow-up for 02f35b1c90.
Replaces https://github.com/systemd/systemd/pull/33231.
It has been mentioned in IPv4Forwarding= and IPv6Forwarding=,
but let's also explain in the settings who imply these settings.
Follow-up for 3976c43092 and
485f5148b3.
For run0 (as opposed to systemd-run in general), connecting to
the system bus (of localhost or container) as a different user
than root and then trying to elevate privilege from that
makes little sense:
https://github.com/systemd/systemd/issues/32997#issuecomment-2127992973
The @ syntax is mostly useful when connecting to the user bus,
which is not a use case for run0. Hence, let's remove the example.
The syntax will be properly refused in #32999.
- mention that /run/machine-id is used if exist.
- mention system.machine_id credential,
- credential, VM uuid, and container uuid are not read when --root=
is specified or running in a chroot environment.
Fixes https://github.com/systemd/systemd/issues/28514.
Quoting https://github.com/systemd/systemd/issues/28514#issuecomment-1831781486:
> Whenever PAM is enabled for a service, we set up the PAM session and then
> fork off a process whose only job is to eventually close the PAM session when
> the service dies. That services we run with service privileges, both to
> minimize attack surface and because we want to use PR_SET_DEATHSIG to be get
> a notification via signal whenever the main process dies. But that only works
> if we have the same credentials as that main process.
>
> Now, if pam_systemd runs inside the PAM stack (which it normally does) it's
> session close hook will ask logind to synchronously end the session via a bus
> call. Currently that call is not accessible to unprivileged clients. And
> that's the part we need to relax: allow users to end their own sessions.
The check is implemented in a way that allows the kill if the sender is in
the target session.
I found 'sudo systemctl --user -M "zbyszek@" is-system-running' to
be a convenient reproducer.
Before:
May 16 16:25:26 x1c systemd[1]: run-u24754.service: Deactivated successfully.
May 16 16:25:26 x1c dbus-broker[1489]: A security policy denied :1.24757 to send method call /org/freedesktop/login1:org.freedesktop.login1.Manager.ReleaseSession to org.freedesktop.login1.
May 16 16:25:26 x1c (sd-pam)[3036470]: pam_systemd(login:session): Failed to release session: Access denied
May 16 16:25:26 x1c systemd[1]: Stopping session-114.scope...
May 16 16:25:26 x1c systemd[1]: session-114.scope: Deactivated successfully.
May 16 16:25:26 x1c systemd[1]: Stopped session-114.scope.
May 16 16:25:26 x1c systemd[1]: session-c151.scope: Deactivated successfully.
May 16 16:25:26 x1c systemd-logind[1513]: Session c151 logged out. Waiting for processes to exit.
May 16 16:25:26 x1c systemd-logind[1513]: Removed session c151.
After:
May 16 17:02:15 x1c systemd[1]: run-u24770.service: Deactivated successfully.
May 16 17:02:15 x1c systemd[1]: Stopping session-115.scope...
May 16 17:02:15 x1c systemd[1]: session-c153.scope: Deactivated successfully.
May 16 17:02:15 x1c systemd[1]: session-115.scope: Deactivated successfully.
May 16 17:02:15 x1c systemd[1]: Stopped session-115.scope.
May 16 17:02:15 x1c systemd-logind[1513]: Session c153 logged out. Waiting for processes to exit.
May 16 17:02:15 x1c systemd-logind[1513]: Removed session c153.
Edit: this seems to also fix https://github.com/systemd/systemd/issues/8598.
It seems that with the call to ReleaseSession, we wait for the pam session
close hooks to finish. I inserted a 'sleep(10)' after the call to ReleaseSession
in pam_systemd, and things block on that, nothing is killed prematurely.
Prompted by #32895
Rather than ordering with each power operation targets,
ordering against shutdown.target which is a valid
synchronization point. This has no effect if soft-reboot
is being performed.
A fixed name is too rigid, let's give users the ability to define
custom drop-in names which at the same time also allows defining
multiple dropins per unit.
We use ~ as the separator because:
- ':' is not allowed in credential names
- '=' is used to separate credential from value in mkosi's --credential
argument.
- '-' is commonly used in filenames
- '@' already has meaning as the unit template specifier which might be
confusing when adding dropins for template units
Like much English text, the systemd documentation uses "may not" in the
sense of both "will possibly not" and "is forbidden to". In many cases
this is OK because the context makes it clear, but in others I felt it
was possible to read the "is forbidden to" sense by mistake: in
particular, I tripped over "the target file may not exist" in
systemd.unit(5) before realizing the correct interpretation.
Use "might not" or "may choose not to" in these cases to make it clear
which sense we mean.
This commit adds the new varlink interface io.systemd.Machine at
/run/systemd/machine/io.systemd.Machine with a single method Register
It supports all combinations of RegisterMachine[WithSSH,WithNetwork] all
under the same method.
Also adds three properties:
- VsockCid: the VSOCK CID of the VM
- SshAddress: the address of the VM in a format SSH can connect to
- SshPrivateKeyPath: the path to the SSH private key to use to connect
to the VM.
GetMachineSSHInfo is essentially a convenience method to query both the
SshAddress and SshPrivateKeyPath properties at once.
In the majority of cases, this is caused by
sleep_supported() returning error. Hence it's
very likely that it would fail again, so
the fallback is not really useful. Instead,
honor the --force option for these verbs.
