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core: populate $REMOTE_ADDR for AF_UNIX sockets

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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
$REMOTE_ADDR, we make this information readily available to the
activated service.
This commit is contained in:
Kamil Szczęk 2024-06-03 17:56:42 +02:00 committed by Luca Boccassi
parent bd6e5b4d93
commit 608bfe76c1
3 changed files with 36 additions and 17 deletions
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13
man/systemd.exec.xml
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@ -4101,8 +4101,17 @@ StandardInputData=V2XigLJyZSBubyBzdHJhbmdlcnMgdG8gbG92ZQpZb3Uga25vdyB0aGUgcnVsZX
<term><varname>$REMOTE_PORT</varname></term>
<listitem><para>If this is a unit started via per-connection socket activation (i.e. via a socket
unit with <varname>Accept=yes</varname>), these environment variables contain the IP address and
port number of the remote peer of the socket connection.</para>
unit with <varname>Accept=yes</varname>), these environment variables contain information about the
remote peer of the socket connection.</para>
<para>For IPv4 and IPv6 connections, <varname>$REMOTE_ADDR</varname> contains the IP address, and
<varname>$REMOTE_PORT</varname> contains the port number of the remote peer.</para>
<para>For <constant>AF_UNIX</constant> socket connections, <varname>$REMOTE_ADDR</varname> contains
either the remote socket's file system path starting with a slash (<literal>/</literal>), its
address in the abstract namespace starting with an at symbol (<literal>@</literal>), or is unset
in case of an unnamed socket. <varname>$REMOTE_PORT</varname> is not set for <constant>AF_UNIX</constant>
sockets.</para>
<xi:include href="version-info.xml" xpointer="v254"/></listitem>
</varlistentry>

9
man/systemd.socket.xml
View File

@ -424,11 +424,16 @@
services (in case of <varname>Accept=</varname><option>yes</option>). See the Description section
above for a more detailed discussion of the naming rules of triggered services.</para>
<para>For IPv4 and IPv6 connections, the <varname>REMOTE_ADDR</varname> environment variable will
contain the remote IP address, and <varname>REMOTE_PORT</varname> will contain the remote port. This
<para>For IPv4 and IPv6 connections, the <varname>$REMOTE_ADDR</varname> environment variable will
contain the remote IP address, and <varname>$REMOTE_PORT</varname> will contain the remote port. This
is the same as the format used by CGI. For <constant>SOCK_RAW</constant>, the port is the IP
protocol.</para>
<para>For <constant>AF_UNIX</constant> socket connections, the <varname>$REMOTE_ADDR</varname>
environment variable will contain either the remote socket's file system path starting with a slash
(<literal>/</literal>) or its address in the abstract namespace starting with an at symbol
(<literal>@</literal>). If the socket is unnamed, <varname>$REMOTE_ADDR</varname> won't be set.</para>
<para>It is recommended to set <varname>CollectMode=inactive-or-failed</varname> for service
instances activated via <varname>Accept=yes</varname>, to ensure that failed connection services are
cleaned up and released from memory, and do not accumulate.</para></listitem>

31
src/core/service.c
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@ -1723,27 +1723,32 @@ static int service_spawn_internal(
* in ENOTCONN), and just use whate we can use. */
if (getpeername(s->socket_fd, &sa.sa, &salen) >= 0 &&
IN_SET(sa.sa.sa_family, AF_INET, AF_INET6, AF_VSOCK)) {
IN_SET(sa.sa.sa_family, AF_INET, AF_INET6, AF_VSOCK, AF_UNIX)) {
_cleanup_free_ char *addr = NULL;
char *t;
unsigned port;
r = sockaddr_pretty(&sa.sa, salen, true, false, &addr);
r = sockaddr_pretty(&sa.sa, salen, /* translate_ipv6= */ true, /* include_port= */ false, &addr);
if (r < 0)
return r;
t = strjoin("REMOTE_ADDR=", addr);
if (!t)
return -ENOMEM;
our_env[n_env++] = t;
if (sa.sa.sa_family != AF_UNIX || IN_SET(addr[0], '/', '@')) {
t = strjoin("REMOTE_ADDR=", addr);
if (!t)
return -ENOMEM;
our_env[n_env++] = t;
}
r = sockaddr_port(&sa.sa, &port);
if (r < 0)
return r;
if (IN_SET(sa.sa.sa_family, AF_INET, AF_INET6, AF_VSOCK)) {
unsigned port;
if (asprintf(&t, "REMOTE_PORT=%u", port) < 0)
return -ENOMEM;
our_env[n_env++] = t;
r = sockaddr_port(&sa.sa, &port);
if (r < 0)
return r;
if (asprintf(&t, "REMOTE_PORT=%u", port) < 0)
return -ENOMEM;
our_env[n_env++] = t;
}
}
}