Add support for DHCP static route options

This adds support for DHCP options 33 and 121: Static Route and
Classless Static Route. To enable this feature, set UseRoutes=true
in .network file. Returned routes are added to the routing table.

src/libsystemd-network/dhcp-lease-internal.h

@@ -32,6 +32,12 @@
 
 #include "sd-dhcp-client.h"
 
+struct sd_dhcp_route {
+        struct in_addr dst_addr;
+        struct in_addr gw_addr;
+        uint8_t dst_prefixlen;
+};
+
 struct sd_dhcp_lease {
         RefCount n_ref;
 
@@ -52,8 +58,9 @@ struct sd_dhcp_lease {
         size_t ntp_size;
         struct in_addr *policy_filter;
         size_t policy_filter_size;
-        struct in_addr *static_route;
+        struct sd_dhcp_route *static_route;
         size_t static_route_size;
+        size_t static_route_allocated;
         uint16_t boot_file_size;
         uint16_t mdr;
         uint16_t mtu;

src/libsystemd-network/dhcp-protocol.h

@@ -132,5 +132,6 @@ enum {
         DHCP_OPTION_RENEWAL_T1_TIME             = 58,
         DHCP_OPTION_REBINDING_T2_TIME           = 59,
         DHCP_OPTION_CLIENT_IDENTIFIER           = 61,
+        DHCP_OPTION_CLASSLESS_STATIC_ROUTE      = 121,
         DHCP_OPTION_END                         = 255,
 };

src/libsystemd-network/network-internal.c

@@ -28,6 +28,7 @@
 #include "siphash24.h"
 #include "libudev-private.h"
 #include "network-internal.h"
+#include "dhcp-lease-internal.h"
 #include "log.h"
 #include "utf8.h"
 #include "util.h"
@@ -432,3 +433,88 @@ int deserialize_in6_addrs(struct in6_addr **ret, size_t *ret_size, const char *s
 
         return 0;
 }
+
+void serialize_dhcp_routes(FILE *f, const char *key, struct sd_dhcp_route *routes, size_t size) {
+        unsigned i;
+
+        assert(f);
+        assert(key);
+        assert(routes);
+        assert(size);
+
+        fprintf(f, "%s=", key);
+
+        for (i = 0; i < size; i++)
+                fprintf(f, "%s/%" PRIu8 ",%s%s", inet_ntoa(routes[i].dst_addr),
+                        routes[i].dst_prefixlen, inet_ntoa(routes[i].gw_addr),
+                        (i < (size - 1)) ? " ": "");
+
+        fputs("\n", f);
+}
+
+int deserialize_dhcp_routes(struct sd_dhcp_route **ret, size_t *ret_size, size_t *ret_allocated, const char *string) {
+        _cleanup_free_ struct sd_dhcp_route *routes = NULL;
+        size_t size = 0, allocated = 0;
+        char *word, *state;
+        size_t len;
+
+        assert(ret);
+        assert(ret_size);
+        assert(ret_allocated);
+        assert(string);
+
+        FOREACH_WORD(word, len, string, state) {
+                /* WORD FORMAT: dst_ip/dst_prefixlen,gw_ip */
+                _cleanup_free_ char* entry;
+                char *tok, *tok_end;
+                unsigned n;
+                int r;
+
+                if (!GREEDY_REALLOC(routes, allocated, size + 1))
+                        return -ENOMEM;
+
+                entry = strndup(word, len);
+
+                tok = entry;
+
+                /* get the subnet */
+                tok_end = strchr(tok, '/');
+                if (!tok_end)
+                        continue;
+                *tok_end = '\0';
+
+                r = inet_aton(tok, &routes[size].dst_addr);
+                if (r == 0)
+                        continue;
+
+                tok = tok_end + 1;
+
+                /* get the prefixlen */
+                tok_end = strchr(tok, ',');
+                if (!tok_end)
+                        continue;
+
+                *tok_end = '\0';
+
+                r = safe_atou(tok, &n);
+                if (r < 0 || n > 32)
+                        continue;
+
+                routes[size].dst_prefixlen = (uint8_t) n;
+                tok = tok_end + 1;
+
+                /* get the gateway */
+                r = inet_aton(tok, &routes[size].gw_addr);
+                if (r == 0)
+                        continue;
+
+                size++;
+        }
+
+        *ret_size = size;
+        *ret_allocated = allocated;
+        *ret = routes;
+        routes = NULL;
+
+        return 0;
+}

src/libsystemd-network/network-internal.h

@@ -70,3 +70,10 @@ const char *net_get_name(struct udev_device *device);
 void serialize_in_addrs(FILE *f, const char *key, struct in_addr *addresses, size_t size);
 int deserialize_in_addrs(struct in_addr **addresses, size_t *size, const char *string);
 int deserialize_in6_addrs(struct in6_addr **addresses, size_t *size, const char *string);
+
+
+/* don't include "dhcp-lease-internal.h" as it causes conflicts between netinet/ip.h and linux/ip.h */
+struct sd_dhcp_route;
+
+void serialize_dhcp_routes(FILE *f, const char *key, struct sd_dhcp_route *routes, size_t size);
+int deserialize_dhcp_routes(struct sd_dhcp_route **ret, size_t *ret_size, size_t *ret_allocated, const char *string);

src/libsystemd-network/sd-dhcp-lease.c

@@ -171,6 +171,22 @@ int sd_dhcp_lease_get_next_server(sd_dhcp_lease *lease, struct in_addr *addr) {
         return 0;
 }
 
+int sd_dhcp_lease_get_routes(sd_dhcp_lease *lease, struct sd_dhcp_route **routes,
+        size_t *routes_size) {
+
+        assert_return(lease, -EINVAL);
+        assert_return(routes, -EINVAL);
+        assert_return(routes_size, -EINVAL);
+
+        if (lease->static_route_size) {
+                *routes = lease->static_route;
+                *routes_size = lease->static_route_size;
+        } else
+                return -ENOENT;
+
+        return 0;
+}
+
 sd_dhcp_lease *sd_dhcp_lease_ref(sd_dhcp_lease *lease) {
         if (lease)
                 assert_se(REFCNT_INC(lease->n_ref) >= 2);
@@ -184,6 +200,7 @@ sd_dhcp_lease *sd_dhcp_lease_unref(sd_dhcp_lease *lease) {
                 free(lease->domainname);
                 free(lease->dns);
                 free(lease->ntp);
+                free(lease->static_route);
                 free(lease);
         }
 
@@ -301,6 +318,111 @@ static int lease_parse_in_addrs_pairs(const uint8_t *option, size_t len, struct
         return lease_parse_in_addrs_aux(option, len, ret, ret_size, 2);
 }
 
+static int class_prefixlen(uint8_t msb_octet, uint8_t *ret) {
+        if (msb_octet < 128)
+                /* Class A */
+                *ret = 8;
+        else if (msb_octet < 192)
+                /* Class B */
+                *ret = 16;
+        else if (msb_octet < 224)
+                /* Class C */
+                *ret = 24;
+        else
+                /* Class D or E -- no subnet mask */
+                return -ERANGE;
+
+        return 0;
+}
+
+static int lease_parse_routes(const uint8_t *option, size_t len, struct sd_dhcp_route **routes,
+        size_t *routes_size, size_t *routes_allocated) {
+
+        struct in_addr addr;
+
+        assert(option);
+        assert(routes);
+        assert(routes_size);
+        assert(routes_allocated);
+
+        if (!len)
+                return 0;
+
+        if (len % 8 != 0)
+                return -EINVAL;
+
+        if (!GREEDY_REALLOC(*routes, *routes_allocated, *routes_size + (len / 8)))
+                return -ENOMEM;
+
+        while (len >= 8) {
+                struct sd_dhcp_route *route = *routes + *routes_size;
+
+                if (class_prefixlen(*option, &route->dst_prefixlen) < 0) {
+                        log_error("Failed to determine destination prefix length from class based IP, ignoring");
+                        continue;
+                }
+
+                lease_parse_be32(option, 4, &addr.s_addr);
+                route->dst_addr = inet_makeaddr(inet_netof(addr), 0);
+                option += 4;
+
+                lease_parse_be32(option, 4, &route->gw_addr.s_addr);
+                option += 4;
+
+                len -= 8;
+                (*routes_size)++;
+        }
+
+        return 0;
+}
+
+/* parses RFC3442 Classless Static Route Option */
+static int lease_parse_classless_routes(const uint8_t *option, size_t len, struct sd_dhcp_route **routes,
+        size_t *routes_size, size_t *routes_allocated) {
+
+        assert(option);
+        assert(routes);
+        assert(routes_size);
+        assert(routes_allocated);
+
+        /* option format: (subnet-mask-width significant-subnet-octets gateway-ip)*  */
+
+        while (len > 0) {
+                uint8_t dst_octets;
+                struct sd_dhcp_route *route;
+
+                if (!GREEDY_REALLOC(*routes, *routes_allocated, *routes_size + 1))
+                    return -ENOMEM;
+
+                route = *routes + *routes_size;
+
+                dst_octets = (*option == 0 ? 0 : ((*option - 1) / 8) + 1);
+                route->dst_prefixlen = *option;
+                option++;
+                len--;
+
+                /* can't have more than 4 octets in IPv4 */
+                if (dst_octets > 4 || len < dst_octets)
+                        return -EINVAL;
+
+                route->dst_addr.s_addr = 0;
+                memcpy(&route->dst_addr.s_addr, option, dst_octets);
+                option += dst_octets;
+                len -= dst_octets;
+
+                if (len < 4)
+                        return -EINVAL;
+
+                lease_parse_be32(option, 4, &route->gw_addr.s_addr);
+                option += 4;
+                len -= 4;
+
+                (*routes_size)++;
+        }
+
+        return 0;
+}
+
 int dhcp_lease_parse_options(uint8_t code, uint8_t len, const uint8_t *option,
                               void *user_data) {
         sd_dhcp_lease *lease = user_data;
@@ -367,7 +489,8 @@ int dhcp_lease_parse_options(uint8_t code, uint8_t len, const uint8_t *option,
                 break;
 
         case DHCP_OPTION_STATIC_ROUTE:
-                r = lease_parse_in_addrs_pairs(option, len, &lease->static_route, &lease->static_route_size);
+                r = lease_parse_routes(option, len, &lease->static_route, &lease->static_route_size,
+                        &lease->static_route_allocated);
                 if (r < 0)
                         return r;
 
@@ -433,6 +556,14 @@ int dhcp_lease_parse_options(uint8_t code, uint8_t len, const uint8_t *option,
                 lease_parse_bool(option, len, &lease->ip_forward_non_local);
 
                 break;
+
+        case DHCP_OPTION_CLASSLESS_STATIC_ROUTE:
+                r = lease_parse_classless_routes(option, len, &lease->static_route, &lease->static_route_size,
+                        &lease->static_route_allocated);
+                if (r < 0)
+                        return r;
+
+                break;
         }
 
         return 0;
@@ -460,6 +591,8 @@ int dhcp_lease_save(sd_dhcp_lease *lease, const char *lease_file) {
         size_t addresses_size;
         const char *string;
         uint16_t mtu;
+        struct sd_dhcp_route *routes;
+        size_t routes_size;
         int r;
 
         assert(lease);
@@ -522,6 +655,10 @@ int dhcp_lease_save(sd_dhcp_lease *lease, const char *lease_file) {
         if (r >= 0)
                 fprintf(f, "ROOT_PATH=%s\n", string);
 
+        r = sd_dhcp_lease_get_routes(lease, &routes, &routes_size);
+        if (r >= 0)
+                serialize_dhcp_routes(f, "ROUTES", routes, routes_size);
+
         r = 0;
 
         fflush(f);
@@ -543,7 +680,7 @@ int dhcp_lease_load(const char *lease_file, sd_dhcp_lease **ret) {
         _cleanup_dhcp_lease_unref_ sd_dhcp_lease *lease = NULL;
         _cleanup_free_ char *address = NULL, *router = NULL, *netmask = NULL,
                             *server_address = NULL, *next_server = NULL,
-                            *dns = NULL, *ntp = NULL, *mtu = NULL;
+                            *dns = NULL, *ntp = NULL, *mtu = NULL, *routes = NULL;
         struct in_addr addr;
         int r;
 
@@ -566,6 +703,7 @@ int dhcp_lease_load(const char *lease_file, sd_dhcp_lease **ret) {
                            "DOMAINNAME", &lease->domainname,
                            "HOSTNAME", &lease->hostname,
                            "ROOT_PATH", &lease->root_path,
+                           "ROUTES", &routes,
                            NULL);
         if (r < 0) {
                 if (r == -ENOENT)
@@ -629,6 +767,13 @@ int dhcp_lease_load(const char *lease_file, sd_dhcp_lease **ret) {
                         lease->mtu = u;
         }
 
+        if (routes) {
+                r = deserialize_dhcp_routes(&lease->static_route, &lease->static_route_size,
+                                &lease->static_route_allocated, routes);
+                if (r < 0)
+                    return r;
+        }
+
         *ret = lease;
         lease = NULL;