Ubuntu 网络管理

ubuntu/debian 中的网络管理

• NetworkManager,使用nmcli查询与操作网络配置
  /run/NetworkManager/no-stub-resolv.conf
  对应命令行例子: nmcli device show
• systemd-networkd,使用netplan的yaml文件来配置网络
  /usr/lib/systemd/systemd-networkd
• systemd-resolved,dns的配置文件
  16.04|20.04 /lib/systemd/systemd-resolved
24.04 /usr/lib/systemd/systemd-resolved
/run/systemd/resolve/resolv.conf
  一般使用命令行systemd-resolve --status 低版本中没有(16.04)

NetworkManager

提供libnm库读取与操作网络配置,对应命令是nmcli
使用c的例子来展示网络信息, 能获取到每个网口DHCP得到的DNS.

#include <NetworkManager.h>
#include <glib.h>
#include <stdio.h>

static char *
ip4_address_as_string (guint32 ip)
{
	char *ip_string;
	struct in_addr tmp_addr;

	tmp_addr.s_addr = ip;
	ip_string = g_malloc0 (INET_ADDRSTRLEN + 1);
	if (!inet_ntop (AF_INET, &tmp_addr, ip_string, INET_ADDRSTRLEN))
		strcpy (ip_string, "(none)");
	return ip_string;
}

int main() {
	GError *error = NULL;
	NMClient *client = nm_client_new(NULL, &error);

	if (error) {
		g_print("Failed to create NetworkManager client: %s\n", error->message);
		g_error_free(error);
		return -1;
	}

	// 获取所有活跃的连接
	GPtrArray *active_connections = nm_client_get_active_connections(client);
	if (active_connections) {
		for (guint i = 0; i < active_connections->len; i++) {
			NMActiveConnection *active_connection = g_ptr_array_index(
					active_connections, i);

			NMConnection *connection = nm_active_connection_get_connection(
					active_connection);
			if (connection) {
				const char *connection_id = nm_connection_get_id(connection);
				g_print("Active Connection ID: %s\n", connection_id);
			}

			// 获取与该活跃连接相关的设备
			GPtrArray *devices = nm_active_connection_get_devices(
					active_connection);
			if (devices) {
				for (guint j = 0; j < devices->len; j++) {
					NMDevice *device = g_ptr_array_index(devices, j);
					const char *device_name = nm_device_get_iface(device);
					g_print("Device: %s\n", device_name);

					// 获取设备的 IPv4 配置
					NMIPConfig *ip4_config = nm_device_get_ip4_config(device);

					if (ip4_config) {
						if (ip4_config) {
							GPtrArray *addresses = nm_ip_config_get_addresses(
									ip4_config);

							for (guint i = 0; i < addresses->len; i++) {
								NMIPAddress *addr =
										(NMIPAddress*) g_ptr_array_index(
												addresses, i);

								const char *str = nm_ip_address_get_address(addr);
								g_print("  IPv4 Address: %s\n", str);
								guint32 hostmask, network, bcast, netmask;

								guint32 addr_bin;

								nm_ip_address_get_address_binary (addr, &addr_bin);
								netmask = nm_utils_ip4_prefix_to_netmask (nm_ip_address_get_prefix (addr));
								network = addr_bin & netmask;
								hostmask = ~netmask;
								bcast = network | hostmask;
								str = ip4_address_as_string (bcast);
								g_print("Broadcast Address:%s\n", str);
								g_free (str);

								str = ip4_address_as_string (netmask);
								g_print("Subnet Mask:%s\n", str);
								g_free (str);
							}

							const char *gateway = nm_ip_config_get_gateway(ip4_config);
							g_print("Gateway:%s\n", gateway);
							const char * const *dns = nm_ip_config_get_nameservers (ip4_config);
							for (i = 0; dns && dns[i] && i < 3; i++) {
								g_print("DNS[%d]:%s\n", i, dns[i]);
							}
						}
					}
				}
			}
		}
	} else {
		g_print("No active connections found.\n");
	}

	g_object_unref(client);
	return 0;
}

netplan

使用systemd-networkd做服务,配置文件在/etc/netplan中

network:
        version: 2
        # 如果renderer是NetworkManager则netplan不会使用systemd-networkd服务也不会启动.
        renderer: networkd
        ethernets:
                enp3s0:
                        dhcp4: yes
                        addresses: []
                        dhcp-identifier: mac
                        optional: yes