gethostname(3) says it's unspecified whether the string is properly terminated
when the hostname is too long. We created a buffer with one extra byte, and it
seems the intent was to let that byte serve as terminator even if we get an
unterminated string from gethostname().
No functional change, just moving a bunch of things around. Before
we needed a rather complicated setup to test hostname_setup(), because
the code was in src/core/. When things are moved to src/shared/
we can just test it as any function.
The test is still "unsafe" because hostname_setup() may modify the
hostname.
The semantics were significantly changed in c779a44222
("hostnamed: Fix the way that static and transient host names interact", Feb. 2014),
but when the dbus api documentation was imported much later, it wasn't properly
adjusted to describe those new semantics.
34293dfafd which added systemd.hostname= also
added new behaviour.
Let's ove various bits and pieces around so that they are in more appropriate
places. Drop recommendations to set the hostname for DHCP or mDNS purposes.
Nowadays we expect tools that want to expose some different hostname to the
outside to manage that internally without affecting visible state. Also drop
mentions of DHCP or mDNS directly setting the hostname, since nowadays network
management software is expected to (and does) go through hostnamed.
Also, add a high-level description of semantics. It glosses over the details of
handling of localhost-style names. Later commits will remove this special handling
anyway.
When someone runs 'nft flush ruleset' in the same net namespace
this will also tear down the systemd nat table.
Unlike iptables -t nat -F, which will remove all rules added by
the systemd iptables backend, iptables has builtin chains that cannot
be deleted. IOW, the next add operation will 'just work'.
In the nftables case however, the entire table gets removed.
When the systemd nat table is removed by an external entity next
attempt to add a set element will yield -ENOENT.
If this happens, recreate the table, and, if successful, re-do
the add operation.
Note that this doesn't protect against external sabotage such as
a running 'while true; nft flush ruleset;done'. However, there is
nothing that could be done short of extending the kernel to allow
tables to be "frozen" or otherwise tied to a process such as
systemd-networkd.
Idea is to use a static ruleset, added when the first attempt to
add a masquerade or dnat rule is made.
The alternative would be to add the ruleset when the init function is called.
The disadvantage is that this enables connection tracking and NAT in the kernel
(as the ruleset needs this to work), which comes with some overhead that might
not be needed (no nspawn usage and no IPMasquerade option set).
There is no additional dependency on the 'nft' userspace binary or other libraries.
sd-netlinks nfnetlink backend is used to modify the nftables ruleset.
The commit message/comments still use nft syntax since that is what
users will see when they use the nft tool to list the ruleset.
The added initial skeleton (added on first fw_add_masquerade/local_dnat
call) looks like this:
table ip io.systemd.nat {
set masq_saddr {
type ipv4_addr
flags interval
elements = { 192.168.59.160/28 }
}
map map_port_ipport {
type inet_proto . inet_service : ipv4_addr . inet_service
elements = { tcp . 2222 : 192.168.59.169 . 22 }
}
chain prerouting {
type nat hook prerouting priority dstnat + 1; policy accept;
fib daddr type local dnat ip addr . port to meta l4proto . th dport map @map_port_ipport
}
chain output {
type nat hook output priority -99; policy accept;
ip daddr != 127.0.0.0/8 oif "lo" dnat ip addr . port to meta l4proto . th dport map @map_port_ipport
}
chain postrouting {
type nat hook postrouting priority srcnat + 1; policy accept;
ip saddr @masq_saddr masquerade
}
}
Next calls to fw_add_masquerade/add_local_dnat will then only add/delete the
element/mapping to masq_saddr and map_port_ipport, i.e. the ruleset doesn't
change -- only the set/map content does.
Running test-firewall-util with this backend gives following output
on a parallel 'nft monitor':
$ nft monitor
add table ip io.systemd.nat
add chain ip io.systemd.nat prerouting { type nat hook prerouting priority dstnat + 1; policy accept; }
add chain ip io.systemd.nat output { type nat hook output priority -99; policy accept; }
add chain ip io.systemd.nat postrouting { type nat hook postrouting priority srcnat + 1; policy accept; }
add set ip io.systemd.nat masq_saddr { type ipv4_addr; flags interval; }
add map ip io.systemd.nat map_port_ipport { type inet_proto . inet_service : ipv4_addr . inet_service; }
add rule ip io.systemd.nat prerouting fib daddr type local dnat ip addr . port to meta l4proto . th dport map @map_port_ipport
add rule ip io.systemd.nat output ip daddr != 127.0.0.0/8 fib daddr type local dnat ip addr . port to meta l4proto . th dport map @map_port_ipport
add rule ip io.systemd.nat postrouting ip saddr @masq_saddr masquerade
add element ip io.systemd.nat masq_saddr { 10.1.2.3 }
add element ip io.systemd.nat masq_saddr { 10.0.2.0/28 }
delete element ip io.systemd.nat masq_saddr { 10.0.2.0/28 }
delete element ip io.systemd.nat masq_saddr { 10.1.2.3 }
add element ip io.systemd.nat map_port_ipport { tcp . 4711 : 1.2.3.4 . 815 }
delete element ip io.systemd.nat map_port_ipport { tcp . 4711 : 1.2.3.4 . 815 }
add element ip io.systemd.nat map_port_ipport { tcp . 4711 : 1.2.3.5 . 815 }
delete element ip io.systemd.nat map_port_ipport { tcp . 4711 : 1.2.3.5 . 815 }
CTRL-C
Things not implemented/supported:
1. Change monitoring. The kernel allows userspace to learn about changes
made by other clients (using nfnetlink notifications). It would be
possible to detect when e.g. someone removes the systemd nat table.
This would need more work. Its also not clear on how to react to
external changes -- it doesn't seem like a good idea to just auto-undo
everthing.
2. 'set masq_saddr' doesn't handle overlaps.
Example:
fw_add_masquerade(true, AF_INET, "10.0.0.0" , 16);
fw_add_masquerade(true, AF_INET, "10.0.0.0" , 8); /* fails */
With the iptables backend the second call works, as it adds an
independent iptables rule.
With the nftables backend, the range 10.0.0.0-10.255.255.255 clashes with
the existing range of 10.0.0.0-10.0.255.255 so 2nd add gets rejected by the
kernel.
This will generate an error message from networkd ("Could not enable IP
masquerading: File exists").
To resolve this it would be needed to either keep track of the added elements
and perform range merging when overlaps are detected.
However, the add erquests are done using the configured network on a
device, so no overlaps should occur in normal setups.
IPv6 support is added in a extra changeset.
Fixes: #13307
Will be used by nftables nfnetlink backend.
It sends a series of netlink messages that form a nftables
update transaction.
The transaction will then generate a series of ack messages
(or an error).
This function will be used to read these acks.
nftables uses a transaction-based netlink model: one netlink write
comes with multiple messages.
A 'BEGIN' message to tell nf_tables/kernel that a new transaction starts.
Then, one more messages to add/delete tables/chains/rules etc.
Lastly, an END message that commits all changes.
This function will be used to send all the individual messages that should
make up a single transaction as a single write.
add nfnetlink_nftables helper functions to:
* open a new nfnetlink socket to kernel
* add tables, chains, rules, sets and maps
* delete/flush table
* add and delete elements from sets/maps
for planned nft backend we have three choices:
- open/close a new nfnetlink socket for every operation
- keep a nfnetlink socket open internally
- expose a opaque fw_ctx and stash all internal data here.
Originally I opted for the 2nd option, but during review it was
suggested to avoid static storage duration because of perceived
problems with threaded applications.
This adds fw_ctx and new/free functions, then converts the existing api
and nspawn and networkd to use it.
Next patch will need to pass two pointers to the callback instead
of just the addr mask. Caller will pass a compound structure, so
make this 'void *userdata' to de-clutter the next patch.
In a nutshell:
1. git mv firewall-util.c firewall-util-iptables.c
2. existing external functions gain _iptables_ in their names
3. firewall-util.c provides old function names
4. build system always compiles firewall-util.c,
firewall-util-iptables.c is conditional instead (libiptc).
5. On first call to any of the 'old' API functions performs
a probe that should return the preferred backend.
In a future step, can add firewall-util-FOOTYPE.c, add its
probe function to firewall-util.c and then have calls to
fw_add_masq/local_dnat handed to the detected backend.
For now, only iptables backend exists, and no special probing
takes place for it, i.e. when systemd was built with iptables,
that will be used. If not, requets to add masquerade/dnat will
fail with same error (-EOPNOTSUPP) as before this change.
For reference, the rules added by the libiptc/iptables backend look like this:
for service export (via systemd-nspawn):
[0:0] -A PREROUTING -p tcp -m tcp --dport $exportedport -m addrtype --dst-type LOCAL -j DNAT --to-destination $containerip:$port
[0:0] -A OUTPUT ! -d 127.0.0.0/8 -p tcp -m tcp --dport $exportedport -m addrtype --dst-type LOCAL -j DNAT --to-destination $containerip:$port
for ip masquerade:
[0:0] -A POSTROUTING -s network/prefix -j MASQUERADE
Make sure we don't add masquerading rules without a explicitly
specified network range we should be masquerading for.
The only caller aside from test case is
networkd-address.c which never passes a NULL source.
As it also passes the network prefix, that should always be > 0 as well.
This causes expected test failure:
Failed to modify firewall: Invalid argument
Failed to modify firewall: Invalid argument
Failed to modify firewall: Invalid argument
Failed to modify firewall: Protocol not available
Failed to modify firewall: Protocol not available
Failed to modify firewall: Protocol not available
Failed to modify firewall: Protocol not available
The failing test cases are amended to expect failure on
NULL source or prefix instead of success.
Upgrading to qemu 5.2 breaks TEST-36-NUMAPOLICY like:
qemu-system-x86_64: total memory for NUMA nodes (0x0) should
equal RAM size (0x20000000)
Use the new (as in >=2014) form of memdev in test 36:
-object memory-backend-ram,id=mem0,size=512M -numa node,memdev=mem0,nodeid=0
Since some target systems are as old as qemu 1.5.3 (CentOS7) but the new
kind to specify was added in qemu 2.1 this needs to add version parsing and
add the argument only when qemu is >=5.2.
Fixes#17986.
Signed-off-by: Christian Ehrhardt <christian.ehrhardt@canonical.com>
This commit extends $SYSTEMD_COLORS to an enum variable (compared to
a simple boolean) which specifies the "colors mode". This means that, in
addition to disabling colors altogether, it's now possible to restrict
the console output to 16 or 256 colors only.
Previously, we'd already have explicit logging for the case where
$XDG_RUNTIME_DIR is not set. Let's also add some explicit logging for
the EPERM/ACCESS case. Let's also in both cases suggest the
--machine=<user>@.host syntax.
And while we are at it, let's remove side-effects from the macro.
By checking for both the EPERM/EACCES case and the $XDG_RUNTIME_DIR case
we will now catch both the cases where people use "su" to issue a
"systemctl --user" operation, and those where they (more correctly, but
still not good enough) call "su -".
Fixes: #17901
So far, the bridge always acted as if "--system" was used, i.e. would
unconditionally connect to the system bus. Let's add "--user" too, to
connect to the users session bus.
This is mostly for completeness' sake.
I wanted to use this when making sd-bus's ability to connect to other
user's D-Bus busses work, but it didn't exist so far. In the interest of
keeping things compatible the implementation in sd-bus will not use the
new "--user" switch, and instead manually construct the right bus path
via "--path=", but we still should add the proper switches, as
preparation for a brighter future, one day.
Zbigniew Jędrzejewski-Szmek