chiark / gitweb /
sd-rtnl: fix size check in sd_rtnl_message_append_string()
[elogind.git] / src / libsystemd / sd-rtnl / rtnl-message.c
index 9558e112af62ce673123a9495569dc6addcf1958..165e84d7a0a1d2cdb11e31f305eed6ba86ab2c5f 100644 (file)
 #include <netinet/ether.h>
 #include <stdbool.h>
 #include <unistd.h>
-#include <linux/netlink.h>
-#include <linux/veth.h>
-#include <linux/if.h>
-#include <linux/ip.h>
-#include <linux/if_tunnel.h>
-#include <linux/if_bridge.h>
 
 #include "util.h"
 #include "refcnt.h"
@@ -42,6 +36,8 @@
 #define GET_CONTAINER(m, i) ((i) < (m)->n_containers ? (struct rtattr*)((uint8_t*)(m)->hdr + (m)->container_offsets[i]) : NULL)
 #define PUSH_CONTAINER(m, new) (m)->container_offsets[(m)->n_containers ++] = (uint8_t*)(new) - (uint8_t*)(m)->hdr;
 
+#define RTA_TYPE(rta) ((rta)->rta_type & NLA_TYPE_MASK)
+
 static int message_new_empty(sd_rtnl *rtnl, sd_rtnl_message **ret) {
         sd_rtnl_message *m;
 
@@ -118,6 +114,24 @@ int sd_rtnl_message_route_set_dst_prefixlen(sd_rtnl_message *m, unsigned char pr
         return 0;
 }
 
+int sd_rtnl_message_route_set_src_prefixlen(sd_rtnl_message *m, unsigned char prefixlen) {
+        struct rtmsg *rtm;
+
+        assert_return(m, -EINVAL);
+        assert_return(m->hdr, -EINVAL);
+        assert_return(rtnl_message_type_is_route(m->hdr->nlmsg_type), -EINVAL);
+
+        rtm = NLMSG_DATA(m->hdr);
+
+        if ((rtm->rtm_family == AF_INET && prefixlen > 32) ||
+            (rtm->rtm_family == AF_INET6 && prefixlen > 128))
+                return -ERANGE;
+
+        rtm->rtm_src_len = prefixlen;
+
+        return 0;
+}
+
 int sd_rtnl_message_route_set_scope(sd_rtnl_message *m, unsigned char scope) {
         struct rtmsg *rtm;
 
@@ -132,13 +146,60 @@ int sd_rtnl_message_route_set_scope(sd_rtnl_message *m, unsigned char scope) {
         return 0;
 }
 
+int sd_rtnl_message_route_get_family(sd_rtnl_message *m, int *family) {
+        struct rtmsg *rtm;
+
+        assert_return(m, -EINVAL);
+        assert_return(m->hdr, -EINVAL);
+        assert_return(rtnl_message_type_is_route(m->hdr->nlmsg_type), -EINVAL);
+        assert_return(family, -EINVAL);
+
+        rtm = NLMSG_DATA(m->hdr);
+
+        *family = rtm->rtm_family;
+
+        return 0;
+}
+
+int sd_rtnl_message_route_get_dst_prefixlen(sd_rtnl_message *m, unsigned char *dst_len) {
+        struct rtmsg *rtm;
+
+        assert_return(m, -EINVAL);
+        assert_return(m->hdr, -EINVAL);
+        assert_return(rtnl_message_type_is_route(m->hdr->nlmsg_type), -EINVAL);
+        assert_return(dst_len, -EINVAL);
+
+        rtm = NLMSG_DATA(m->hdr);
+
+        *dst_len = rtm->rtm_dst_len;
+
+        return 0;
+}
+
+int sd_rtnl_message_route_get_src_prefixlen(sd_rtnl_message *m, unsigned char *src_len) {
+        struct rtmsg *rtm;
+
+        assert_return(m, -EINVAL);
+        assert_return(m->hdr, -EINVAL);
+        assert_return(rtnl_message_type_is_route(m->hdr->nlmsg_type), -EINVAL);
+        assert_return(src_len, -EINVAL);
+
+        rtm = NLMSG_DATA(m->hdr);
+
+        *src_len = rtm->rtm_src_len;
+
+        return 0;
+}
+
 int sd_rtnl_message_new_route(sd_rtnl *rtnl, sd_rtnl_message **ret,
-                              uint16_t nlmsg_type, unsigned char rtm_family) {
+                              uint16_t nlmsg_type, int rtm_family,
+                              unsigned char rtm_protocol) {
         struct rtmsg *rtm;
         int r;
 
         assert_return(rtnl_message_type_is_route(nlmsg_type), -EINVAL);
-        assert_return(rtm_family == AF_INET || rtm_family == AF_INET6, -EINVAL);
+        assert_return((nlmsg_type == RTM_GETROUTE && rtm_family == AF_UNSPEC) ||
+                      rtm_family == AF_INET || rtm_family == AF_INET6, -EINVAL);
         assert_return(ret, -EINVAL);
 
         r = message_new(rtnl, ret, nlmsg_type);
@@ -154,7 +215,60 @@ int sd_rtnl_message_new_route(sd_rtnl *rtnl, sd_rtnl_message **ret,
         rtm->rtm_scope = RT_SCOPE_UNIVERSE;
         rtm->rtm_type = RTN_UNICAST;
         rtm->rtm_table = RT_TABLE_MAIN;
-        rtm->rtm_protocol = RTPROT_BOOT;
+        rtm->rtm_protocol = rtm_protocol;
+
+        return 0;
+}
+
+int sd_rtnl_message_neigh_get_family(sd_rtnl_message *m, int *family) {
+        struct ndmsg *ndm;
+
+        assert_return(m, -EINVAL);
+        assert_return(m->hdr, -EINVAL);
+        assert_return(rtnl_message_type_is_neigh(m->hdr->nlmsg_type), -EINVAL);
+        assert_return(family, -EINVAL);
+
+        ndm = NLMSG_DATA(m->hdr);
+
+        *family = ndm->ndm_family;
+
+        return 0;
+}
+
+int sd_rtnl_message_neigh_get_ifindex(sd_rtnl_message *m, int *index) {
+        struct ndmsg *ndm;
+
+        assert_return(m, -EINVAL);
+        assert_return(m->hdr, -EINVAL);
+        assert_return(rtnl_message_type_is_neigh(m->hdr->nlmsg_type), -EINVAL);
+        assert_return(index, -EINVAL);
+
+        ndm = NLMSG_DATA(m->hdr);
+
+        *index = ndm->ndm_ifindex;
+
+        return 0;
+}
+
+int sd_rtnl_message_new_neigh(sd_rtnl *rtnl, sd_rtnl_message **ret, uint16_t nlmsg_type, int index, int ndm_family) {
+        struct ndmsg *ndm;
+        int r;
+
+        assert_return(rtnl_message_type_is_neigh(nlmsg_type), -EINVAL);
+        assert_return(ndm_family == AF_INET || ndm_family == AF_INET6, -EINVAL);
+        assert_return(ret, -EINVAL);
+
+        r = message_new(rtnl, ret, nlmsg_type);
+        if (r < 0)
+                return r;
+
+        if (nlmsg_type == RTM_NEWNEIGH)
+                (*ret)->hdr->nlmsg_flags |= NLM_F_CREATE | NLM_F_APPEND;
+
+        ndm = NLMSG_DATA((*ret)->hdr);
+
+        ndm->ndm_family = ndm_family;
+        ndm->ndm_ifindex = index;
 
         return 0;
 }
@@ -189,6 +303,20 @@ int sd_rtnl_message_link_set_type(sd_rtnl_message *m, unsigned type) {
         return 0;
 }
 
+int sd_rtnl_message_link_set_family(sd_rtnl_message *m, unsigned family) {
+        struct ifinfomsg *ifi;
+
+        assert_return(m, -EINVAL);
+        assert_return(m->hdr, -EINVAL);
+        assert_return(rtnl_message_type_is_link(m->hdr->nlmsg_type), -EINVAL);
+
+        ifi = NLMSG_DATA(m->hdr);
+
+        ifi->ifi_family = family;
+
+        return 0;
+}
+
 int sd_rtnl_message_new_link(sd_rtnl *rtnl, sd_rtnl_message **ret,
                              uint16_t nlmsg_type, int index) {
         struct ifinfomsg *ifi;
@@ -216,9 +344,10 @@ int sd_rtnl_message_new_link(sd_rtnl *rtnl, sd_rtnl_message **ret,
 int sd_rtnl_message_request_dump(sd_rtnl_message *m, int dump) {
         assert_return(m, -EINVAL);
         assert_return(m->hdr, -EINVAL);
-        assert_return(m->hdr->nlmsg_type == RTM_GETLINK ||
-                      m->hdr->nlmsg_type == RTM_GETADDR ||
-                      m->hdr->nlmsg_type == RTM_GETROUTE,
+        assert_return(m->hdr->nlmsg_type == RTM_GETLINK  ||
+                      m->hdr->nlmsg_type == RTM_GETADDR  ||
+                      m->hdr->nlmsg_type == RTM_GETROUTE ||
+                      m->hdr->nlmsg_type == RTM_GETNEIGH,
                       -EINVAL);
 
         if (dump)
@@ -275,7 +404,7 @@ int sd_rtnl_message_addr_set_scope(sd_rtnl_message *m, unsigned char scope) {
         return 0;
 }
 
-int sd_rtnl_message_addr_get_family(sd_rtnl_message *m, unsigned char *family) {
+int sd_rtnl_message_addr_get_family(sd_rtnl_message *m, int *family) {
         struct ifaddrmsg *ifa;
 
         assert_return(m, -EINVAL);
@@ -352,7 +481,7 @@ int sd_rtnl_message_addr_get_ifindex(sd_rtnl_message *m, int *ifindex) {
 
 int sd_rtnl_message_new_addr(sd_rtnl *rtnl, sd_rtnl_message **ret,
                              uint16_t nlmsg_type, int index,
-                             unsigned char family) {
+                             int family) {
         struct ifaddrmsg *ifa;
         int r;
 
@@ -383,7 +512,7 @@ int sd_rtnl_message_new_addr(sd_rtnl *rtnl, sd_rtnl_message **ret,
 }
 
 int sd_rtnl_message_new_addr_update(sd_rtnl *rtnl, sd_rtnl_message **ret,
-                             int index, unsigned char family) {
+                             int index, int family) {
         int r;
 
         r = sd_rtnl_message_new_addr(rtnl, ret, RTM_NEWADDR, index, family);
@@ -464,6 +593,21 @@ int sd_rtnl_message_link_get_flags(sd_rtnl_message *m, unsigned *flags) {
         return 0;
 }
 
+int sd_rtnl_message_link_get_type(sd_rtnl_message *m, unsigned *type) {
+        struct ifinfomsg *ifi;
+
+        assert_return(m, -EINVAL);
+        assert_return(m->hdr, -EINVAL);
+        assert_return(rtnl_message_type_is_link(m->hdr->nlmsg_type), -EINVAL);
+        assert_return(type, -EINVAL);
+
+        ifi = NLMSG_DATA(m->hdr);
+
+        *type = ifi->ifi_type;
+
+        return 0;
+}
+
 /* If successful the updated message will be correctly aligned, if
    unsuccessful the old message is untouched. */
 static int add_rtattr(sd_rtnl_message *m, unsigned short type, const void *data, size_t data_length) {
@@ -515,7 +659,6 @@ static int add_rtattr(sd_rtnl_message *m, unsigned short type, const void *data,
                 /* if no data was passed, make sure we still initialize the padding
                    note that we can have data_length > 0 (used by some containers) */
                 padding = RTA_DATA(rta);
-                data_length = 0;
         }
 
         /* make sure also the padding at the end of the message is initialized */
@@ -557,8 +700,8 @@ int sd_rtnl_message_append_string(sd_rtnl_message *m, unsigned short type, const
                 size = (size_t)r;
 
         if (size) {
-                length = strnlen(data, size);
-                if (length >= size)
+                length = strnlen(data, size+1);
+                if (length > size)
                         return -EINVAL;
         } else
                 length = strlen(data);
@@ -714,7 +857,7 @@ int sd_rtnl_message_open_container(sd_rtnl_message *m, unsigned short type) {
         if (r < 0)
                 return r;
 
-        r = add_rtattr(m, type, NULL, size);
+        r = add_rtattr(m, type | NLA_F_NESTED, NULL, size);
         if (r < 0)
                 return r;
 
@@ -786,10 +929,12 @@ int rtnl_message_read_internal(sd_rtnl_message *m, unsigned short type, void **d
         return RTA_PAYLOAD(rta);
 }
 
-int sd_rtnl_message_read_string(sd_rtnl_message *m, unsigned short type, char **data) {
+int sd_rtnl_message_read_string(sd_rtnl_message *m, unsigned short type, const char **data) {
         int r;
         void *attr_data;
 
+        assert_return(m, -EINVAL);
+
         r = message_attribute_has_type(m, type, NLA_STRING);
         if (r < 0)
                 return r;
@@ -800,7 +945,8 @@ int sd_rtnl_message_read_string(sd_rtnl_message *m, unsigned short type, char **
         else if (strnlen(attr_data, r) >= (size_t) r)
                 return -EIO;
 
-        *data = (char *) attr_data;
+        if (data)
+                *data = (const char *) attr_data;
 
         return 0;
 }
@@ -809,6 +955,8 @@ int sd_rtnl_message_read_u8(sd_rtnl_message *m, unsigned short type, uint8_t *da
         int r;
         void *attr_data;
 
+        assert_return(m, -EINVAL);
+
         r = message_attribute_has_type(m, type, NLA_U8);
         if (r < 0)
                 return r;
@@ -819,7 +967,8 @@ int sd_rtnl_message_read_u8(sd_rtnl_message *m, unsigned short type, uint8_t *da
         else if ((size_t) r < sizeof(uint8_t))
                 return -EIO;
 
-        *data = *(uint8_t *) attr_data;
+        if (data)
+                *data = *(uint8_t *) attr_data;
 
         return 0;
 }
@@ -828,6 +977,8 @@ int sd_rtnl_message_read_u16(sd_rtnl_message *m, unsigned short type, uint16_t *
         int r;
         void *attr_data;
 
+        assert_return(m, -EINVAL);
+
         r = message_attribute_has_type(m, type, NLA_U16);
         if (r < 0)
                 return r;
@@ -838,7 +989,8 @@ int sd_rtnl_message_read_u16(sd_rtnl_message *m, unsigned short type, uint16_t *
         else if ((size_t) r < sizeof(uint16_t))
                 return -EIO;
 
-        *data = *(uint16_t *) attr_data;
+        if (data)
+                *data = *(uint16_t *) attr_data;
 
         return 0;
 }
@@ -847,6 +999,8 @@ int sd_rtnl_message_read_u32(sd_rtnl_message *m, unsigned short type, uint32_t *
         int r;
         void *attr_data;
 
+        assert_return(m, -EINVAL);
+
         r = message_attribute_has_type(m, type, NLA_U32);
         if (r < 0)
                 return r;
@@ -857,7 +1011,8 @@ int sd_rtnl_message_read_u32(sd_rtnl_message *m, unsigned short type, uint32_t *
         else if ((size_t)r < sizeof(uint32_t))
                 return -EIO;
 
-        *data = *(uint32_t *) attr_data;
+        if (data)
+                *data = *(uint32_t *) attr_data;
 
         return 0;
 }
@@ -866,6 +1021,8 @@ int sd_rtnl_message_read_ether_addr(sd_rtnl_message *m, unsigned short type, str
         int r;
         void *attr_data;
 
+        assert_return(m, -EINVAL);
+
         r = message_attribute_has_type(m, type, NLA_ETHER_ADDR);
         if (r < 0)
                 return r;
@@ -876,7 +1033,8 @@ int sd_rtnl_message_read_ether_addr(sd_rtnl_message *m, unsigned short type, str
         else if ((size_t)r < sizeof(struct ether_addr))
                 return -EIO;
 
-        memcpy(data, attr_data, sizeof(struct ether_addr));
+        if (data)
+                memcpy(data, attr_data, sizeof(struct ether_addr));
 
         return 0;
 }
@@ -885,6 +1043,8 @@ int sd_rtnl_message_read_cache_info(sd_rtnl_message *m, unsigned short type, str
         int r;
         void *attr_data;
 
+        assert_return(m, -EINVAL);
+
         r = message_attribute_has_type(m, type, NLA_CACHE_INFO);
         if (r < 0)
                 return r;
@@ -895,7 +1055,8 @@ int sd_rtnl_message_read_cache_info(sd_rtnl_message *m, unsigned short type, str
         else if ((size_t)r < sizeof(struct ifa_cacheinfo))
                 return -EIO;
 
-        memcpy(info, attr_data, sizeof(struct ifa_cacheinfo));
+        if (info)
+                memcpy(info, attr_data, sizeof(struct ifa_cacheinfo));
 
         return 0;
 }
@@ -904,6 +1065,8 @@ int sd_rtnl_message_read_in_addr(sd_rtnl_message *m, unsigned short type, struct
         int r;
         void *attr_data;
 
+        assert_return(m, -EINVAL);
+
         r = message_attribute_has_type(m, type, NLA_IN_ADDR);
         if (r < 0)
                 return r;
@@ -914,7 +1077,8 @@ int sd_rtnl_message_read_in_addr(sd_rtnl_message *m, unsigned short type, struct
         else if ((size_t)r < sizeof(struct in_addr))
                 return -EIO;
 
-        memcpy(data, attr_data, sizeof(struct in_addr));
+        if (data)
+                memcpy(data, attr_data, sizeof(struct in_addr));
 
         return 0;
 }
@@ -923,6 +1087,8 @@ int sd_rtnl_message_read_in6_addr(sd_rtnl_message *m, unsigned short type, struc
         int r;
         void *attr_data;
 
+        assert_return(m, -EINVAL);
+
         r = message_attribute_has_type(m, type, NLA_IN_ADDR);
         if (r < 0)
                 return r;
@@ -933,7 +1099,8 @@ int sd_rtnl_message_read_in6_addr(sd_rtnl_message *m, unsigned short type, struc
         else if ((size_t)r < sizeof(struct in6_addr))
                 return -EIO;
 
-        memcpy(data, attr_data, sizeof(struct in6_addr));
+        if (data)
+                memcpy(data, attr_data, sizeof(struct in6_addr));
 
         return 0;
 }
@@ -962,7 +1129,7 @@ int sd_rtnl_message_enter_container(sd_rtnl_message *m, unsigned short type) {
                         return r;
         } else if (nl_type->type == NLA_UNION) {
                 const NLTypeSystemUnion *type_system_union;
-                char *key;
+                const char *key;
 
                 r = type_system_get_type_system_union(m->container_type_system[m->n_containers],
                                                       &type_system_union,
@@ -1027,13 +1194,20 @@ uint32_t rtnl_message_get_serial(sd_rtnl_message *m) {
         return m->hdr->nlmsg_seq;
 }
 
+int sd_rtnl_message_is_error(sd_rtnl_message *m) {
+        assert_return(m, 0);
+        assert_return(m->hdr, 0);
+
+        return m->hdr->nlmsg_type == NLMSG_ERROR;
+}
+
 int sd_rtnl_message_get_errno(sd_rtnl_message *m) {
         struct nlmsgerr *err;
 
         assert_return(m, -EINVAL);
         assert_return(m->hdr, -EINVAL);
 
-        if (m->hdr->nlmsg_type != NLMSG_ERROR)
+        if (!sd_rtnl_message_is_error(m))
                 return 0;
 
         err = NLMSG_DATA(m->hdr);
@@ -1057,7 +1231,7 @@ int rtnl_message_parse(sd_rtnl_message *m,
         *rta_tb_size = max + 1;
 
         for (; RTA_OK(rta, rt_len); rta = RTA_NEXT(rta, rt_len)) {
-                type = rta->rta_type;
+                type = RTA_TYPE(rta);
 
                 /* if the kernel is newer than the headers we used
                    when building, we ignore out-of-range attributes
@@ -1098,8 +1272,9 @@ int socket_write_message(sd_rtnl *nl, sd_rtnl_message *m) {
         return k;
 }
 
-static int socket_recv_message(int fd, struct iovec *iov, bool peek) {
-        uint8_t cred_buffer[CMSG_SPACE(sizeof(struct ucred))];
+static int socket_recv_message(int fd, struct iovec *iov, uint32_t *_group, bool peek) {
+        uint8_t cred_buffer[CMSG_SPACE(sizeof(struct ucred)) +
+                            CMSG_SPACE(sizeof(struct nl_pktinfo))];
         struct msghdr msg = {
                 .msg_iov = iov,
                 .msg_iovlen = 1,
@@ -1107,6 +1282,7 @@ static int socket_recv_message(int fd, struct iovec *iov, bool peek) {
                 .msg_controllen = sizeof(cred_buffer),
         };
         struct cmsghdr *cmsg;
+        uint32_t group = 0;
         bool auth = false;
         int r;
 
@@ -1114,10 +1290,13 @@ static int socket_recv_message(int fd, struct iovec *iov, bool peek) {
         assert(iov);
 
         r = recvmsg(fd, &msg, MSG_TRUNC | (peek ? MSG_PEEK : 0));
-        if (r < 0)
+        if (r < 0) {
                 /* no data */
+                if (errno == ENOBUFS)
+                        log_debug("rtnl: kernel receive buffer overrun");
+
                 return (errno == EAGAIN) ? 0 : -errno;
-        else if (r == 0)
+        else if (r == 0)
                 /* connection was closed by the kernel */
                 return -ECONNRESET;
 
@@ -1128,10 +1307,15 @@ static int socket_recv_message(int fd, struct iovec *iov, bool peek) {
                         struct ucred *ucred = (void *)CMSG_DATA(cmsg);
 
                         /* from the kernel */
-                        if (ucred->uid == 0 && ucred->pid == 0) {
+                        if (ucred->uid == 0 && ucred->pid == 0)
                                 auth = true;
-                                break;
-                        }
+                } else if (cmsg->cmsg_level == SOL_NETLINK &&
+                           cmsg->cmsg_type == NETLINK_PKTINFO &&
+                           cmsg->cmsg_len == CMSG_LEN(sizeof(struct nl_pktinfo))) {
+                        struct nl_pktinfo *pktinfo = (void *)CMSG_DATA(cmsg);
+
+                        /* multi-cast group */
+                        group = pktinfo->group;
                 }
         }
 
@@ -1139,6 +1323,9 @@ static int socket_recv_message(int fd, struct iovec *iov, bool peek) {
                 /* not from the kernel, ignore */
                 return 0;
 
+        if (group)
+                *_group = group;
+
         return r;
 }
 
@@ -1150,6 +1337,7 @@ static int socket_recv_message(int fd, struct iovec *iov, bool peek) {
 int socket_read_message(sd_rtnl *rtnl) {
         _cleanup_rtnl_message_unref_ sd_rtnl_message *first = NULL;
         struct iovec iov = {};
+        uint32_t group = 0;
         bool multi_part = false, done = false;
         struct nlmsghdr *new_msg;
         size_t len;
@@ -1161,7 +1349,7 @@ int socket_read_message(sd_rtnl *rtnl) {
         assert(rtnl->rbuffer_allocated >= sizeof(struct nlmsghdr));
 
         /* read nothing, just get the pending message size */
-        r = socket_recv_message(rtnl->fd, &iov, true);
+        r = socket_recv_message(rtnl->fd, &iov, &group, true);
         if (r <= 0)
                 return r;
         else
@@ -1177,7 +1365,7 @@ int socket_read_message(sd_rtnl *rtnl) {
         iov.iov_len = rtnl->rbuffer_allocated;
 
         /* read the pending message */
-        r = socket_recv_message(rtnl->fd, &iov, false);
+        r = socket_recv_message(rtnl->fd, &iov, &group, false);
         if (r <= 0)
                 return r;
         else
@@ -1199,11 +1387,11 @@ int socket_read_message(sd_rtnl *rtnl) {
                 }
         }
 
-        for (new_msg = rtnl->rbuffer; NLMSG_OK(new_msg, len); new_msg = NLMSG_NEXT(new_msg, len)) {
+        for (new_msg = rtnl->rbuffer; NLMSG_OK(new_msg, len) && !done; new_msg = NLMSG_NEXT(new_msg, len)) {
                 _cleanup_rtnl_message_unref_ sd_rtnl_message *m = NULL;
                 const NLType *nl_type;
 
-                if (new_msg->nlmsg_pid && new_msg->nlmsg_pid != rtnl->sockaddr.nl.nl_pid)
+                if (!group && new_msg->nlmsg_pid != rtnl->sockaddr.nl.nl_pid)
                         /* not broadcast and not for us */
                         continue;
 
@@ -1214,7 +1402,8 @@ int socket_read_message(sd_rtnl *rtnl) {
                 if (new_msg->nlmsg_type == NLMSG_DONE) {
                         /* finished reading multi-part message */
                         done = true;
-                        break;
+
+                        continue;
                 }
 
                 /* check that we support this message type */
@@ -1228,8 +1417,10 @@ int socket_read_message(sd_rtnl *rtnl) {
                 }
 
                 /* check that the size matches the message type */
-                if (new_msg->nlmsg_len < NLMSG_LENGTH(nl_type->size))
+                if (new_msg->nlmsg_len < NLMSG_LENGTH(nl_type->size)) {
+                        log_debug("sd-rtnl: message larger than expected, dropping");
                         continue;
+                }
 
                 r = message_new_empty(rtnl, &m);
                 if (r < 0)