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nspawn: allow user-specified MAC address on container side

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Introduce the environment variable SYSTEMD_NSPAWN_NETWORK_MAC to allow
user-specified MAC address on container side.
This commit is contained in:
Raul Cheleguini 2023-10-03 23:06:38 -03:00 committed by Luca Boccassi
parent 2e53544c76
commit 813dbff4d5
4 changed files with 27 additions and 6 deletions
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6
docs/ENVIRONMENT.md
View file

@ -170,6 +170,12 @@ All tools:
friends. This is equivalent to passing `--suppress-sync=yes` on the
`systemd-nspawn` command line.
* `$SYSTEMD_NSPAWN_NETWORK_MAC=...` — if set, allows users to set a specific MAC
address for a container, ensuring that it uses the provided value instead of
generating a random one. It is effective when used with `--network-veth`. The
expected format is six groups of two hexadecimal digits separated by colons,
e.g. `SYSTEMD_NSPAWN_NETWORK_MAC=12:34:56:78:90:AB`
`systemd-logind`:
* `$SYSTEMD_BYPASS_HIBERNATION_MEMORY_CHECK=1` — if set, report that

12
src/nspawn/nspawn-network.c
View file

@ -236,7 +236,8 @@ static int shorten_ifname(char *ifname) {
int setup_veth(const char *machine_name,
pid_t pid,
char iface_name[IFNAMSIZ],
bool bridge) {
bool bridge,
struct ether_addr *provided_mac) {
_cleanup_(sd_netlink_unrefp) sd_netlink *rtnl = NULL;
struct ether_addr mac_host, mac_container;
@ -255,9 +256,12 @@ int setup_veth(const char *machine_name,
if (r > 0)
a = strjoina(bridge ? "vb-" : "ve-", machine_name);
r = generate_mac(machine_name, &mac_container, CONTAINER_HASH_KEY, 0);
if (r < 0)
return log_error_errno(r, "Failed to generate predictable MAC address for container side: %m");
if (ether_addr_is_null(provided_mac)){
r = generate_mac(machine_name, &mac_container, CONTAINER_HASH_KEY, 0);
if (r < 0)
return log_error_errno(r, "Failed to generate predictable MAC address for container side: %m");
} else
mac_container = *provided_mac;
r = generate_mac(machine_name, &mac_host, HOST_HASH_KEY, 0);
if (r < 0)

4
src/nspawn/nspawn-network.h
View file

@ -5,9 +5,11 @@
#include <stdbool.h>
#include <sys/types.h>
#include "ether-addr-util.h"
int test_network_interfaces_initialized(char **iface_pairs);
int setup_veth(const char *machine_name, pid_t pid, char iface_name[IFNAMSIZ], bool bridge);
int setup_veth(const char *machine_name, pid_t pid, char iface_name[IFNAMSIZ], bool bridge, struct ether_addr *provided_mac);
int setup_veth_extra(const char *machine_name, pid_t pid, char **pairs);
int setup_bridge(const char *veth_name, const char *bridge_name, bool create);

11
src/nspawn/nspawn.c
View file

@ -24,6 +24,7 @@
#include "sd-id128.h"
#include "alloc-util.h"
#include "ether-addr-util.h"
#include "barrier.h"
#include "base-filesystem.h"
#include "blkid-util.h"
@ -188,6 +189,7 @@ static char **arg_network_veth_extra = NULL;
static char *arg_network_bridge = NULL;
static char *arg_network_zone = NULL;
static char *arg_network_namespace_path = NULL;
struct ether_addr arg_network_provided_mac = {};
static PagerFlags arg_pager_flags = 0;
static unsigned long arg_personality = PERSONALITY_INVALID;
static char *arg_image = NULL;
@ -668,6 +670,13 @@ static int parse_environment(void) {
if (e)
arg_container_service_name = e;
e = getenv("SYSTEMD_NSPAWN_NETWORK_MAC");
if (e) {
r = parse_ether_addr(e, &arg_network_provided_mac);
if (r < 0)
return log_error_errno(r, "Failed to parse provided MAC address via environment variable");
}
r = getenv_bool("SYSTEMD_SUPPRESS_SYNC");
if (r >= 0)
arg_suppress_sync = r;
@ -4978,7 +4987,7 @@ static int run_container(
if (arg_network_veth) {
r = setup_veth(arg_machine, *pid, veth_name,
arg_network_bridge || arg_network_zone);
arg_network_bridge || arg_network_zone, &arg_network_provided_mac);
if (r < 0)
return r;
else if (r > 0)