Merge pull request #21041 from yuwata/network-bpf-neighbor

network: introduce BPF to reject netlink messages about non-static neighbor

src/libsystemd/sd-netlink/sd-netlink.c

@@ -1023,3 +1023,18 @@ int sd_netlink_add_match(
         return netlink_add_match_internal(rtnl, ret_slot, groups, n_groups, type, 0, callback,
                                           destroy_callback, userdata, description);
 }
+
+int sd_netlink_attach_filter(sd_netlink *nl, size_t len, struct sock_filter *filter) {
+        assert_return(nl, -EINVAL);
+        assert_return(len == 0 || filter, -EINVAL);
+
+        if (setsockopt(nl->fd, SOL_SOCKET,
+                       len == 0 ? SO_DETACH_FILTER : SO_ATTACH_FILTER,
+                       &(struct sock_fprog) {
+                               .len = len,
+                               .filter = filter,
+                       }, sizeof(struct sock_fprog)) < 0)
+                return -errno;
+
+        return 0;
+}

src/network/networkd-manager.c

@@ -263,6 +263,40 @@ static int manager_connect_genl(Manager *m) {
         return 0;
 }
 
+static int manager_setup_rtnl_filter(Manager *manager) {
+        struct sock_filter filter[] = {
+                /* Check the packet length. */
+                BPF_STMT(BPF_LD + BPF_W + BPF_LEN, 0),                                      /* A <- packet length */
+                BPF_JUMP(BPF_JMP + BPF_JGE + BPF_K, sizeof(struct nlmsghdr), 1, 0),         /* A (packet length) >= sizeof(struct nlmsghdr) ? */
+                BPF_STMT(BPF_RET + BPF_K, 0),                                               /* reject */
+                /* Always accept multipart message. */
+                BPF_STMT(BPF_LD + BPF_H + BPF_ABS, offsetof(struct nlmsghdr, nlmsg_flags)), /* A <- message flags */
+                BPF_JUMP(BPF_JMP + BPF_JSET + BPF_K, htobe16(NLM_F_MULTI), 0, 1),           /* message flags has NLM_F_MULTI ? */
+                BPF_STMT(BPF_RET + BPF_K, UINT32_MAX),                                      /* accept */
+                /* Accept all message types except for RTM_NEWNEIGH or RTM_DELNEIGH. */
+                BPF_STMT(BPF_LD + BPF_H + BPF_ABS, offsetof(struct nlmsghdr, nlmsg_type)),  /* A <- message type */
+                BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, htobe16(RTM_NEWNEIGH), 2, 0),           /* message type == RTM_NEWNEIGH ? */
+                BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, htobe16(RTM_DELNEIGH), 1, 0),           /* message type == RTM_DELNEIGH ? */
+                BPF_STMT(BPF_RET + BPF_K, UINT32_MAX),                                      /* accept */
+                /* Check the packet length. */
+                BPF_STMT(BPF_LD + BPF_W + BPF_LEN, 0),                                      /* A <- packet length */
+                BPF_JUMP(BPF_JMP + BPF_JGE + BPF_K, sizeof(struct nlmsghdr) + sizeof(struct ndmsg), 1, 0),
+                                                                                            /* packet length >= sizeof(struct nlmsghdr) + sizeof(struct ndmsg) ? */
+                BPF_STMT(BPF_RET + BPF_K, 0),                                               /* reject */
+                /* Reject the message when the neighbor state does not have NUD_PERMANENT flag. */
+                BPF_STMT(BPF_LD + BPF_H + BPF_ABS, sizeof(struct nlmsghdr) + offsetof(struct ndmsg, ndm_state)),
+                                                                                            /* A <- neighbor state */
+                BPF_JUMP(BPF_JMP + BPF_JSET + BPF_K, htobe16(NUD_PERMANENT), 1, 0),         /* neighbor state has NUD_PERMANENT ? */
+                BPF_STMT(BPF_RET + BPF_K, 0),                                               /* reject */
+                BPF_STMT(BPF_RET + BPF_K, UINT32_MAX),                                      /* accept */
+        };
+
+        assert(manager);
+        assert(manager->rtnl);
+
+        return sd_netlink_attach_filter(manager->rtnl, ELEMENTSOF(filter), filter);
+}
+
 static int manager_connect_rtnl(Manager *m) {
         int fd, r;
 
@@ -337,7 +371,7 @@ static int manager_connect_rtnl(Manager *m) {
         if (r < 0)
                 return r;
 
-        return 0;
+        return manager_setup_rtnl_filter(m);
 }
 
 static int manager_dirty_handler(sd_event_source *s, void *userdata) {

src/systemd/sd-netlink.h

@@ -21,6 +21,7 @@
 #include <inttypes.h>
 #include <net/ethernet.h>
 #include <netinet/in.h>
+#include <linux/filter.h>
 #include <linux/neighbour.h>
 #include <linux/rtnetlink.h>
 
@@ -68,6 +69,7 @@ int sd_netlink_add_match(sd_netlink *nl, sd_netlink_slot **ret_slot, uint16_t ma
 
 int sd_netlink_attach_event(sd_netlink *nl, sd_event *e, int64_t priority);
 int sd_netlink_detach_event(sd_netlink *nl);
+int sd_netlink_attach_filter(sd_netlink *nl, size_t len, struct sock_filter *filter);
 
 /* message */
 int sd_netlink_message_append_string(sd_netlink_message *m, unsigned short type, const char *data);

test/test-network/systemd-networkd-tests.py

@@ -21,8 +21,9 @@ networkd_ci_path='/run/networkd-ci'
 network_sysctl_ipv6_path='/proc/sys/net/ipv6/conf'
 network_sysctl_ipv4_path='/proc/sys/net/ipv4/conf'
 
-dnsmasq_pid_file='/run/networkd-ci/test-test-dnsmasq.pid'
-dnsmasq_log_file='/run/networkd-ci/test-dnsmasq-log-file'
+dnsmasq_pid_file='/run/networkd-ci/test-dnsmasq.pid'
+dnsmasq_log_file='/run/networkd-ci/test-dnsmasq.log'
+dnsmasq_lease_file='/run/networkd-ci/test-dnsmasq.lease'
 
 systemd_lib_paths=['/usr/lib/systemd', '/lib/systemd']
 which_paths=':'.join(systemd_lib_paths + os.getenv('PATH', os.defpath).lstrip(':').split(':'))
@@ -474,10 +475,10 @@ def remove_networkd_conf_dropin(dropins):
             os.remove(os.path.join(networkd_conf_dropin_path, dropin))
 
 def start_dnsmasq(additional_options='', ipv4_range='192.168.5.10,192.168.5.200', ipv6_range='2600::10,2600::20', lease_time='1h'):
-    dnsmasq_command = f'dnsmasq -8 /var/run/networkd-ci/test-dnsmasq-log-file --log-queries=extra --log-dhcp --pid-file=/var/run/networkd-ci/test-test-dnsmasq.pid --conf-file=/dev/null --interface=veth-peer --enable-ra --dhcp-range={ipv6_range},{lease_time} --dhcp-range={ipv4_range},{lease_time} -R --dhcp-leasefile=/var/run/networkd-ci/lease --dhcp-option=26,1492 --dhcp-option=option:router,192.168.5.1 --port=0 ' + additional_options
+    dnsmasq_command = f'dnsmasq -8 {dnsmasq_log_file} --log-queries=extra --log-dhcp --pid-file={dnsmasq_pid_file} --conf-file=/dev/null --interface=veth-peer --enable-ra --dhcp-range={ipv6_range},{lease_time} --dhcp-range={ipv4_range},{lease_time} -R --dhcp-leasefile={dnsmasq_lease_file} --dhcp-option=26,1492 --dhcp-option=option:router,192.168.5.1 --port=0 ' + additional_options
     check_output(dnsmasq_command)
 
-def stop_dnsmasq(pid_file):
+def stop_by_pid_file(pid_file):
     if os.path.exists(pid_file):
         with open(pid_file, 'r') as f:
             pid = f.read().rstrip(' \t\r\n\0')
@@ -485,6 +486,9 @@ def stop_dnsmasq(pid_file):
 
         os.remove(pid_file)
 
+def stop_dnsmasq():
+    stop_by_pid_file(dnsmasq_pid_file)
+
 def search_words_in_dnsmasq_log(words, show_all=False):
     if os.path.exists(dnsmasq_log_file):
         with open (dnsmasq_log_file) as in_file:
@@ -498,11 +502,11 @@ def search_words_in_dnsmasq_log(words, show_all=False):
                     return True
     return False
 
-def remove_lease_file():
-    if os.path.exists(os.path.join(networkd_ci_path, 'lease')):
-        os.remove(os.path.join(networkd_ci_path, 'lease'))
+def remove_dnsmasq_lease_file():
+    if os.path.exists(dnsmasq_lease_file):
+        os.remove(dnsmasq_lease_file)
 
-def remove_log_file():
+def remove_dnsmasq_log_file():
     if os.path.exists(dnsmasq_log_file):
         os.remove(dnsmasq_log_file)
 
@@ -4034,14 +4038,16 @@ class NetworkdDHCPClientTests(unittest.TestCase, Utilities):
         'static.network']
 
     def setUp(self):
-        stop_dnsmasq(dnsmasq_pid_file)
+        stop_dnsmasq()
+        remove_dnsmasq_lease_file()
+        remove_dnsmasq_log_file()
         remove_links(self.links)
         stop_networkd(show_logs=False)
 
     def tearDown(self):
-        stop_dnsmasq(dnsmasq_pid_file)
-        remove_lease_file()
-        remove_log_file()
+        stop_dnsmasq()
+        remove_dnsmasq_lease_file()
+        remove_dnsmasq_log_file()
         remove_links(self.links)
         remove_unit_from_networkd_path(self.units)
         stop_networkd(show_logs=True)
@@ -4092,7 +4098,7 @@ class NetworkdDHCPClientTests(unittest.TestCase, Utilities):
         self.assertRegex(output, r'192.168.5.6 proto dhcp scope link src 192.168.5.181 metric 1024')
         self.assertRegex(output, r'192.168.5.7 proto dhcp scope link src 192.168.5.181 metric 1024')
 
-        stop_dnsmasq(dnsmasq_pid_file)
+        stop_dnsmasq()
         start_dnsmasq(additional_options='--dhcp-option=option:dns-server,192.168.5.1,192.168.5.7,192.168.5.8', lease_time='2m')
 
         # Sleep for 120 sec as the dnsmasq minimum lease time can only be set to 120
@@ -4330,7 +4336,7 @@ class NetworkdDHCPClientTests(unittest.TestCase, Utilities):
         self.assertRegex(output, r'192.168.6.0/24 proto static')
         self.assertRegex(output, r'192.168.7.0/24 proto static')
 
-        stop_dnsmasq(dnsmasq_pid_file)
+        stop_dnsmasq()
         start_dnsmasq(ipv4_range='192.168.5.210,192.168.5.220', lease_time='2m')
 
         # Sleep for 120 sec as the dnsmasq minimum lease time can only be set to 120
@@ -4363,7 +4369,7 @@ class NetworkdDHCPClientTests(unittest.TestCase, Utilities):
         self.assertRegex(output, r'2600::/64 proto ra metric 1024')
         self.assertRegex(output, r'2600:0:0:1::/64 proto static metric 1024 pref medium')
 
-        stop_dnsmasq(dnsmasq_pid_file)
+        stop_dnsmasq()
         start_dnsmasq(ipv6_range='2600::30,2600::40', lease_time='2m')
 
         # Sleep for 120 sec as the dnsmasq minimum lease time can only be set to 120
@@ -4393,7 +4399,7 @@ class NetworkdDHCPClientTests(unittest.TestCase, Utilities):
         self.assertRegex(output, r'192.168.5.*')
 
         # Stopping dnsmasq as networkd won't be allowed to renew the DHCP lease.
-        stop_dnsmasq(dnsmasq_pid_file)
+        stop_dnsmasq()
 
         # Sleep for 120 sec as the dnsmasq minimum lease time can only be set to 120
         print('Wait for the dynamic address to be expired')
@@ -4443,7 +4449,7 @@ class NetworkdDHCPClientTests(unittest.TestCase, Utilities):
         print(output)
         self.assertRegex(output, r'192.168.5.*')
 
-        stop_dnsmasq(dnsmasq_pid_file)
+        stop_dnsmasq()
         check_output('systemctl stop systemd-networkd.socket')
         check_output('systemctl stop systemd-networkd.service')
 
@@ -4686,7 +4692,7 @@ class NetworkdDHCPClientTests(unittest.TestCase, Utilities):
         self.assertRegex(output, f'default via 192.168.5.1 proto dhcp src {address1} metric 1024')
         self.assertRegex(output, f'192.168.5.1 proto dhcp scope link src {address1} metric 1024')
 
-        stop_dnsmasq(dnsmasq_pid_file)
+        stop_dnsmasq()
         start_dnsmasq(ipv4_range='192.168.5.200,192.168.5.250', lease_time='2m')
 
         print('Wait for the dynamic address to be expired')
@@ -4839,7 +4845,6 @@ class NetworkdIPv6PrefixTests(unittest.TestCase, Utilities):
         stop_networkd(show_logs=False)
 
     def tearDown(self):
-        remove_log_file()
         remove_links(self.links)
         remove_unit_from_networkd_path(self.units)
         stop_networkd(show_logs=True)
@@ -4928,7 +4933,6 @@ class NetworkdMTUTests(unittest.TestCase, Utilities):
         stop_networkd(show_logs=False)
 
     def tearDown(self):
-        remove_log_file()
         remove_links(self.links)
         remove_unit_from_networkd_path(self.units)
         stop_networkd(show_logs=True)