networkd: add minimal IP forwarding and masquerading support to .network files

This adds two new settings to networkd's .network files: IPForwarding=yes and IPMasquerade=yes. The former controls the "forwarding" sysctl setting of the interface, thus controlling whether IP forwarding shall be enabled on the specific interface. The latter controls whether a firewall rule shall be installed that exposes traffic coming from the interface as coming from the local host to all other interfaces. This also enables both options by default for container network interfaces, thus making "systemd-nspawn --network-veth" have network connectivity out of the box.
2015-01-13 13:55:15 +01:00
parent 76917807eb
commit 5a8bcb674f
10 changed files with 232 additions and 70 deletions
@@ -21,13 +21,13 @@

 #include <net/if.h>

-#include "networkd.h"
-#include "networkd-link.h"
-
 #include "utf8.h"
 #include "util.h"
 #include "conf-parser.h"
+#include "fw-util.h"
 #include "network-internal.h"
+#include "networkd.h"
+#include "networkd-link.h"

 static void address_init(Address *address) {
        assert(address);
@@ -103,6 +103,54 @@ void address_free(Address *address) {
        free(address);
 }

+int address_establish(Address *address, Link *link) {
+        bool masq;
+        int r;
+
+        assert(address);
+        assert(link);
+
+        masq = link->network &&
+                link->network->ip_masquerade &&
+                address->family == AF_INET &&
+                address->scope < RT_SCOPE_LINK;
+
+        /* Add firewall entry if this is requested */
+        if (address->ip_forward_done != masq) {
+                union in_addr_union masked = address->in_addr;
+                in_addr_mask(address->family, &masked, address->prefixlen);
+
+                r = fw_add_masquerade(masq, AF_INET, 0, &masked, address->prefixlen, NULL, NULL, 0);
+                if (r < 0)
+                        log_link_warning_errno(link, r, "Could not enable IP masquerading: %m");
+
+                address->ip_forward_done = masq;
+        }
+
+        return 0;
+}
+
+int address_release(Address *address, Link *link) {
+        int r;
+
+        assert(address);
+        assert(link);
+
+        /* Remove masquerading firewall entry if it was added */
+        if (address->ip_forward_done) {
+                union in_addr_union masked = address->in_addr;
+                in_addr_mask(address->family, &masked, address->prefixlen);
+
+                r = fw_add_masquerade(false, AF_INET, 0, &masked, address->prefixlen, NULL, NULL, 0);
+                if (r < 0)
+                        log_link_warning_errno(link, r, "Failed to disable IP masquerading: %m");
+
+                address->ip_forward_done = false;
+        }
+
+        return 0;
+}
+
 int address_drop(Address *address, Link *link,
                 sd_rtnl_message_handler_t callback) {
        _cleanup_rtnl_message_unref_ sd_rtnl_message *req = NULL;
@@ -115,6 +163,8 @@ int address_drop(Address *address, Link *link,
        assert(link->manager);
        assert(link->manager->rtnl);

+        address_release(address, link);
+
        r = sd_rtnl_message_new_addr(link->manager->rtnl, &req, RTM_DELADDR,
                                     link->ifindex, address->family);
        if (r < 0)
@@ -333,6 +383,8 @@ int address_configure(Address *address, Link *link,

        link_ref(link);

+        address_establish(address, link);
+
        return 0;
 }

@@ -549,8 +601,7 @@ bool address_equal(Address *a1, Address *a2) {
                        return (b1 >> (32 - a1->prefixlen)) == (b2 >> (32 - a1->prefixlen));
                }

-        case AF_INET6:
-        {
+        case AF_INET6: {
                uint64_t *b1, *b2;

                b1 = (uint64_t*)&a1->in_addr.in6;
@@ -558,6 +609,7 @@ bool address_equal(Address *a1, Address *a2) {

                return (((b1[0] ^ b2[0]) | (b1[1] ^ b2[1])) == 0UL);
        }
+
        default:
                assert_not_reached("Invalid address family");
        }
@@ -23,16 +23,16 @@
 #include <linux/if.h>
 #include <unistd.h>

-#include "networkd-link.h"
-#include "networkd-netdev.h"
-#include "libudev-private.h"
-#include "udev-util.h"
 #include "util.h"
 #include "virt.h"
+#include "fileio.h"
 #include "bus-util.h"
+#include "udev-util.h"
+#include "libudev-private.h"
 #include "network-internal.h"
+#include "networkd-link.h"
+#include "networkd-netdev.h"
 #include "conf-parser.h"
-
 #include "dhcp-lease-internal.h"

 static bool link_dhcp6_enabled(Link *link) {
@@ -82,12 +82,22 @@ static bool link_lldp_enabled(Link *link) {
        if (!link->network)
                return false;

-        if(link->network->bridge)
+        if (link->network->bridge)
                return false;

        return link->network->lldp;
 }

+static bool link_ip_forward_enabled(Link *link) {
+        if (link->flags & IFF_LOOPBACK)
+                return false;
+
+        if (!link->network)
+                return false;
+
+        return link->network->ip_forward;
+}
+
 #define FLAG_STRING(string, flag, old, new) \
        (((old ^ new) & flag) \
                ? ((old & flag) ? (" -" string) : (" +" string)) \
@@ -653,9 +663,7 @@ static int link_enter_set_addresses(Link *link) {
        LIST_FOREACH(addresses, ad, link->network->static_addresses) {
                r = address_configure(ad, link, &address_handler);
                if (r < 0) {
-                        log_link_warning(link,
-                                         "could not set addresses: %s",
-                                         strerror(-r));
+                        log_link_warning_errno(link, r, "Could not set addresses: %m");
                        link_enter_failed(link);
                        return r;
                }
@@ -1217,6 +1225,18 @@ static int link_enter_join_netdev(Link *link) {
        return 0;
 }

+static int link_set_ip_forward(Link *link) {
+        const char *p = NULL;
+        int r;
+
+        p = strappenda("/proc/sys/net/ipv4/conf/", link->ifname, "/forwarding");
+        r = write_string_file_no_create(p, link_ip_forward_enabled(link) ? "1" : "0");
+        if (r < 0)
+                log_link_warning_errno(link, r, "Cannot configure IP forwarding for interface: %m");
+
+        return 0;
+}
+
 static int link_configure(Link *link) {
        int r;

@@ -1228,6 +1248,10 @@ static int link_configure(Link *link) {
        if (r < 0)
                return r;

+        r = link_set_ip_forward(link);
+        if (r < 0)
+                return r;
+
        if (link_ipv4ll_enabled(link)) {
                r = ipv4ll_configure(link);
                if (r < 0)
@@ -1364,16 +1388,27 @@ int link_initialized(Link *link, struct udev_device *device) {
        return 0;
 }

+static Address* link_get_equal_address(Link *link, Address *needle) {
+        Address *i;
+
+        assert(link);
+        assert(needle);
+
+        LIST_FOREACH(addresses, i, link->addresses)
+                if (address_equal(i, needle))
+                        return i;
+
+        return NULL;
+}
+
 int link_rtnl_process_address(sd_rtnl *rtnl, sd_rtnl_message *message, void *userdata) {
        Manager *m = userdata;
        Link *link = NULL;
        uint16_t type;
        _cleanup_address_free_ Address *address = NULL;
-        Address *ad;
-        char buf[INET6_ADDRSTRLEN];
-        char valid_buf[FORMAT_TIMESPAN_MAX];
+        Address *existing;
+        char buf[INET6_ADDRSTRLEN], valid_buf[FORMAT_TIMESPAN_MAX];
        const char *valid_str = NULL;
-        bool address_dropped = false;
        int r, ifindex;

        assert(rtnl);
@@ -1415,50 +1450,42 @@ int link_rtnl_process_address(sd_rtnl *rtnl, sd_rtnl_message *message, void *use

        r = sd_rtnl_message_addr_get_family(message, &address->family);
        if (r < 0 || !IN_SET(address->family, AF_INET, AF_INET6)) {
-                log_link_warning(link,
-                                 "rtnl: received address with invalid family, ignoring");
+                log_link_warning(link, "rtnl: received address with invalid family, ignoring");
                return 0;
        }

        r = sd_rtnl_message_addr_get_prefixlen(message, &address->prefixlen);
        if (r < 0) {
-                log_link_warning(link,
-                                 "rtnl: received address with invalid prefixlen, ignoring");
+                log_link_warning(link, "rtnl: received address with invalid prefixlen, ignoring");
                return 0;
        }

        r = sd_rtnl_message_addr_get_scope(message, &address->scope);
        if (r < 0) {
-                log_link_warning(link,
-                                 "rtnl: received address with invalid scope, ignoring");
+                log_link_warning(link, "rtnl: received address with invalid scope, ignoring");
                return 0;
        }

        r = sd_rtnl_message_addr_get_flags(message, &address->flags);
        if (r < 0) {
-                log_link_warning(link,
-                                 "rtnl: received address with invalid flags, ignoring");
+                log_link_warning(link, "rtnl: received address with invalid flags, ignoring");
                return 0;
        }

        switch (address->family) {
        case AF_INET:
-                r = sd_rtnl_message_read_in_addr(message, IFA_LOCAL,
-                                                 &address->in_addr.in);
+                r = sd_rtnl_message_read_in_addr(message, IFA_LOCAL, &address->in_addr.in);
                if (r < 0) {
-                        log_link_warning(link,
-                                         "rtnl: received address without valid address, ignoring");
+                        log_link_warning(link, "rtnl: received address without valid address, ignoring");
                        return 0;
                }

                break;

        case AF_INET6:
-                r = sd_rtnl_message_read_in6_addr(message, IFA_ADDRESS,
-                                                  &address->in_addr.in6);
+                r = sd_rtnl_message_read_in6_addr(message, IFA_ADDRESS, &address->in_addr.in6);
                if (r < 0) {
-                        log_link_warning(link,
-                                         "rtnl: received address without valid address, ignoring");
+                        log_link_warning(link, "rtnl: received address without valid address, ignoring");
                        return 0;
                }

@@ -1468,14 +1495,12 @@ int link_rtnl_process_address(sd_rtnl *rtnl, sd_rtnl_message *message, void *use
                assert_not_reached("invalid address family");
        }

-        if (!inet_ntop(address->family, &address->in_addr, buf,
-                       INET6_ADDRSTRLEN)) {
+        if (!inet_ntop(address->family, &address->in_addr, buf, INET6_ADDRSTRLEN)) {
                log_link_warning(link, "could not print address");
                return 0;
        }

-        r = sd_rtnl_message_read_cache_info(message, IFA_CACHEINFO,
-                                            &address->cinfo);
+        r = sd_rtnl_message_read_cache_info(message, IFA_CACHEINFO, &address->cinfo);
        if (r >= 0) {
                if (address->cinfo.ifa_valid == CACHE_INFO_INFINITY_LIFE_TIME)
                        valid_str = "ever";
@@ -1485,43 +1510,40 @@ int link_rtnl_process_address(sd_rtnl *rtnl, sd_rtnl_message *message, void *use
                                                    USEC_PER_SEC);
        }

-        LIST_FOREACH(addresses, ad, link->addresses) {
-                if (address_equal(ad, address)) {
-                        LIST_REMOVE(addresses, link->addresses, ad);
-
-                        address_free(ad);
-
-                        address_dropped = true;
-
-                        break;
-                }
-        }
+        existing = link_get_equal_address(link, address);

        switch (type) {
        case RTM_NEWADDR:
-                if (!address_dropped)
-                        log_link_debug(link, "added address: %s/%u (valid for %s)",
-                                       buf, address->prefixlen, valid_str);
-                else
-                        log_link_debug(link, "updated address: %s/%u (valid for %s)",
-                                       buf, address->prefixlen, valid_str);
+                if (existing) {
+                        log_link_debug(link, "Updating address: %s/%u (valid for %s)", buf, address->prefixlen, valid_str);

-                LIST_PREPEND(addresses, link->addresses, address);
-                address = NULL;

-                link_save(link);
+                        existing->scope = address->scope;
+                        existing->flags = address->flags;
+                        existing->cinfo = address->cinfo;

-                break;
-        case RTM_DELADDR:
-                if (address_dropped) {
-                        log_link_debug(link, "removed address: %s/%u (valid for %s)",
-                                       buf, address->prefixlen, valid_str);
+                } else {
+                        log_link_debug(link, "Adding address: %s/%u (valid for %s)", buf, address->prefixlen, valid_str);
+
+                        LIST_PREPEND(addresses, link->addresses, address);
+                        address_establish(address, link);
+
+                        address = NULL;

                        link_save(link);
+                }
+
+                break;
+
+        case RTM_DELADDR:
+
+                if (existing) {
+                        log_link_debug(link, "Removing address: %s/%u (valid for %s)", buf, address->prefixlen, valid_str);
+                        address_release(existing, link);
+                        LIST_REMOVE(addresses, link->addresses, existing);
+                        address_free(existing);
                } else
-                        log_link_warning(link,
-                                         "removing non-existent address: %s/%u (valid for %s)",
-                                         buf, address->prefixlen, valid_str);
+                        log_link_warning(link, "Removing non-existent address: %s/%u (valid for %s)", buf, address->prefixlen, valid_str);

                break;
        default:
@@ -44,6 +44,8 @@ Network.Domains,             config_parse_domains,               0,
 Network.DNS,                 config_parse_strv,                  0,                             offsetof(Network, dns)
 Network.LLMNR,               config_parse_llmnr,                 0,                             offsetof(Network, llmnr)
 Network.NTP,                 config_parse_strv,                  0,                             offsetof(Network, ntp)
+Network.IPForward,           config_parse_bool,                  0,                             offsetof(Network, ip_forward)
+Network.IPMasquerade,        config_parse_bool,                  0,                             offsetof(Network, ip_masquerade)
 Address.Address,             config_parse_address,               0,                             0
 Address.Peer,                config_parse_address,               0,                             0
 Address.Broadcast,           config_parse_broadcast,             0,                             0
@@ -22,14 +22,14 @@
 #include <ctype.h>
 #include <net/if.h>

-#include "networkd.h"
-#include "networkd-netdev.h"
-#include "networkd-link.h"
-#include "network-internal.h"
 #include "path-util.h"
 #include "conf-files.h"
 #include "conf-parser.h"
 #include "util.h"
+#include "networkd.h"
+#include "networkd-netdev.h"
+#include "networkd-link.h"
+#include "network-internal.h"

 static int network_load_one(Manager *manager, const char *filename) {
        _cleanup_network_free_ Network *network = NULL;
@@ -109,6 +109,10 @@ static int network_load_one(Manager *manager, const char *filename) {
        if (r < 0)
                return r;

+        /* IPMasquerade=yes implies IPForward=yes */
+        if (network->ip_masquerade)
+                network->ip_forward = true;
+
        LIST_PREPEND(networks, manager->networks, network);

        LIST_FOREACH(routes, route, network->static_routes) {
@@ -120,6 +120,9 @@ struct Network {

        unsigned cost;

+        bool ip_masquerade;
+        bool ip_forward;
+
        struct ether_addr *mac;
        unsigned mtu;

@@ -157,6 +160,8 @@ struct Address {
        union in_addr_union in_addr;
        union in_addr_union in_addr_peer;

+        bool ip_forward_done;
+
        LIST_FIELDS(Address, addresses);
 };

@@ -326,6 +331,8 @@ void address_free(Address *address);
 int address_configure(Address *address, Link *link, sd_rtnl_message_handler_t callback);
 int address_update(Address *address, Link *link, sd_rtnl_message_handler_t callback);
 int address_drop(Address *address, Link *link, sd_rtnl_message_handler_t callback);
+int address_establish(Address *address, Link *link);
+int address_release(Address *address, Link *link);
 bool address_equal(Address *a1, Address *a2);

 DEFINE_TRIVIAL_CLEANUP_FUNC(Address*, address_free);