Adding upstream version 255.4.upstream/255.4

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1421 insertions, 0 deletions

diff --git a/src/libsystemd/sd-netlink/netlink-message.c b/src/libsystemd/sd-netlink/netlink-message.c
new file mode 100644
index 0000000..000a50e
--- /dev/null
+++ b/src/libsystemd/sd-netlink/netlink-message.c
@@ -0,0 +1,1421 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include <netinet/in.h>
+#include <stdbool.h>
+#include <unistd.h>
+
+#include "sd-netlink.h"
+
+#include "alloc-util.h"
+#include "format-util.h"
+#include "memory-util.h"
+#include "netlink-internal.h"
+#include "netlink-types.h"
+#include "netlink-util.h"
+#include "socket-util.h"
+#include "strv.h"
+
+#define GET_CONTAINER(m, i) ((struct rtattr*)((uint8_t*)(m)->hdr + (m)->containers[i].offset))
+
+#define RTA_TYPE(rta) ((rta)->rta_type & NLA_TYPE_MASK)
+#define RTA_FLAGS(rta) ((rta)->rta_type & ~NLA_TYPE_MASK)
+
+int message_new_empty(sd_netlink *nl, sd_netlink_message **ret) {
+        sd_netlink_message *m;
+
+        assert(nl);
+        assert(ret);
+
+        /* Note that 'nl' is currently unused, if we start using it internally we must take care to
+         * avoid problems due to mutual references between buses and their queued messages. See sd-bus. */
+
+        m = new(sd_netlink_message, 1);
+        if (!m)
+                return -ENOMEM;
+
+        *m = (sd_netlink_message) {
+                .n_ref = 1,
+                .protocol = nl->protocol,
+                .sealed = false,
+        };
+
+        *ret = m;
+        return 0;
+}
+
+int message_new_full(
+                sd_netlink *nl,
+                uint16_t nlmsg_type,
+                const NLAPolicySet *policy_set,
+                size_t header_size,
+                sd_netlink_message **ret) {
+
+        _cleanup_(sd_netlink_message_unrefp) sd_netlink_message *m = NULL;
+        size_t size;
+        int r;
+
+        assert(nl);
+        assert(policy_set);
+        assert(ret);
+
+        size = NLMSG_SPACE(header_size);
+        assert(size >= sizeof(struct nlmsghdr));
+
+        r = message_new_empty(nl, &m);
+        if (r < 0)
+                return r;
+
+        m->containers[0].policy_set = policy_set;
+
+        m->hdr = malloc0(size);
+        if (!m->hdr)
+                return -ENOMEM;
+
+        m->hdr->nlmsg_flags = NLM_F_REQUEST | NLM_F_ACK;
+        m->hdr->nlmsg_len = size;
+        m->hdr->nlmsg_type = nlmsg_type;
+
+        *ret = TAKE_PTR(m);
+        return 0;
+}
+
+int message_new(sd_netlink *nl, sd_netlink_message **ret, uint16_t nlmsg_type) {
+        const NLAPolicySet *policy_set;
+        size_t size;
+        int r;
+
+        assert_return(nl, -EINVAL);
+        assert_return(ret, -EINVAL);
+
+        r = netlink_get_policy_set_and_header_size(nl, nlmsg_type, &policy_set, &size);
+        if (r < 0)
+                return r;
+
+        return message_new_full(nl, nlmsg_type, policy_set, size, ret);
+}
+
+int message_new_synthetic_error(sd_netlink *nl, int error, uint32_t serial, sd_netlink_message **ret) {
+        struct nlmsgerr *err;
+        int r;
+
+        assert(error <= 0);
+
+        r = message_new(nl, ret, NLMSG_ERROR);
+        if (r < 0)
+                return r;
+
+        message_seal(*ret);
+        (*ret)->hdr->nlmsg_seq = serial;
+
+        err = NLMSG_DATA((*ret)->hdr);
+        err->error = error;
+
+        return 0;
+}
+
+int sd_netlink_message_set_request_dump(sd_netlink_message *m, int dump) {
+        assert_return(m, -EINVAL);
+        assert_return(m->hdr, -EINVAL);
+        assert_return(m->protocol != NETLINK_ROUTE ||
+                      IN_SET(m->hdr->nlmsg_type,
+                             RTM_GETLINK, RTM_GETLINKPROP, RTM_GETADDR, RTM_GETROUTE, RTM_GETNEIGH,
+                             RTM_GETRULE, RTM_GETADDRLABEL, RTM_GETNEXTHOP, RTM_GETQDISC, RTM_GETTCLASS),
+                      -EINVAL);
+
+        SET_FLAG(m->hdr->nlmsg_flags, NLM_F_DUMP, dump);
+
+        return 0;
+}
+
+DEFINE_TRIVIAL_REF_FUNC(sd_netlink_message, sd_netlink_message);
+
+sd_netlink_message* sd_netlink_message_unref(sd_netlink_message *m) {
+        while (m && --m->n_ref == 0) {
+                unsigned i;
+
+                free(m->hdr);
+
+                for (i = 0; i <= m->n_containers; i++)
+                        free(m->containers[i].attributes);
+
+                sd_netlink_message *t = m;
+                m = m->next;
+                free(t);
+        }
+
+        return NULL;
+}
+
+int sd_netlink_message_get_type(sd_netlink_message *m, uint16_t *ret) {
+        assert_return(m, -EINVAL);
+        assert_return(ret, -EINVAL);
+
+        *ret = m->hdr->nlmsg_type;
+
+        return 0;
+}
+
+int sd_netlink_message_set_flags(sd_netlink_message *m, uint16_t flags) {
+        assert_return(m, -EINVAL);
+        assert_return(flags != 0, -EINVAL);
+
+        m->hdr->nlmsg_flags = flags;
+
+        return 0;
+}
+
+int sd_netlink_message_is_broadcast(sd_netlink_message *m) {
+        assert_return(m, -EINVAL);
+
+        return m->multicast_group != 0;
+}
+
+/* If successful the updated message will be correctly aligned, if unsuccessful the old message is untouched. */
+static int add_rtattr(sd_netlink_message *m, uint16_t attr_type, const void *data, size_t data_length) {
+        size_t message_length;
+        struct nlmsghdr *new_hdr;
+        struct rtattr *rta;
+        int offset;
+
+        assert(m);
+        assert(m->hdr);
+        assert(!m->sealed);
+        assert(NLMSG_ALIGN(m->hdr->nlmsg_len) == m->hdr->nlmsg_len);
+        assert(!data || data_length > 0);
+
+        /* get the new message size (with padding at the end) */
+        message_length = m->hdr->nlmsg_len + RTA_SPACE(data_length);
+
+        /* buffer should be smaller than both one page or 8K to be accepted by the kernel */
+        if (message_length > MIN(page_size(), 8192UL))
+                return -ENOBUFS;
+
+        /* realloc to fit the new attribute */
+        new_hdr = realloc(m->hdr, message_length);
+        if (!new_hdr)
+                return -ENOMEM;
+        m->hdr = new_hdr;
+
+        /* get pointer to the attribute we are about to add */
+        rta = (struct rtattr *) ((uint8_t *) m->hdr + m->hdr->nlmsg_len);
+
+        rtattr_append_attribute_internal(rta, attr_type, data, data_length);
+
+        /* if we are inside containers, extend them */
+        for (unsigned i = 0; i < m->n_containers; i++)
+                GET_CONTAINER(m, i)->rta_len += RTA_SPACE(data_length);
+
+        /* update message size */
+        offset = m->hdr->nlmsg_len;
+        m->hdr->nlmsg_len = message_length;
+
+        /* return old message size */
+        return offset;
+}
+
+static int message_attribute_has_type(sd_netlink_message *m, size_t *ret_size, uint16_t attr_type, NLAType type) {
+        const NLAPolicy *policy;
+
+        assert(m);
+
+        policy = policy_set_get_policy(m->containers[m->n_containers].policy_set, attr_type);
+        if (!policy)
+                return -EOPNOTSUPP;
+
+        if (policy_get_type(policy) != type)
+                return -EINVAL;
+
+        if (ret_size)
+                *ret_size = policy_get_size(policy);
+        return 0;
+}
+
+int sd_netlink_message_append_string(sd_netlink_message *m, uint16_t attr_type, const char *data) {
+        size_t length, size;
+        int r;
+
+        assert_return(m, -EINVAL);
+        assert_return(!m->sealed, -EPERM);
+        assert_return(data, -EINVAL);
+
+        r = message_attribute_has_type(m, &size, attr_type, NETLINK_TYPE_STRING);
+        if (r < 0)
+                return r;
+
+        if (size) {
+                length = strnlen(data, size+1);
+                if (length > size)
+                        return -EINVAL;
+        } else
+                length = strlen(data);
+
+        r = add_rtattr(m, attr_type, data, length + 1);
+        if (r < 0)
+                return r;
+
+        return 0;
+}
+
+int sd_netlink_message_append_strv(sd_netlink_message *m, uint16_t attr_type, const char* const *data) {
+        size_t length, size;
+        int r;
+
+        assert_return(m, -EINVAL);
+        assert_return(!m->sealed, -EPERM);
+        assert_return(data, -EINVAL);
+
+        r = message_attribute_has_type(m, &size, attr_type, NETLINK_TYPE_STRING);
+        if (r < 0)
+                return r;
+
+        STRV_FOREACH(p, data) {
+                if (size) {
+                        length = strnlen(*p, size+1);
+                        if (length > size)
+                                return -EINVAL;
+                } else
+                        length = strlen(*p);
+
+                r = add_rtattr(m, attr_type, *p, length + 1);
+                if (r < 0)
+                        return r;
+        }
+
+        return 0;
+}
+
+int sd_netlink_message_append_flag(sd_netlink_message *m, uint16_t attr_type) {
+        size_t size;
+        int r;
+
+        assert_return(m, -EINVAL);
+        assert_return(!m->sealed, -EPERM);
+
+        r = message_attribute_has_type(m, &size, attr_type, NETLINK_TYPE_FLAG);
+        if (r < 0)
+                return r;
+
+        r = add_rtattr(m, attr_type, NULL, 0);
+        if (r < 0)
+                return r;
+
+        return 0;
+}
+
+int sd_netlink_message_append_u8(sd_netlink_message *m, uint16_t attr_type, uint8_t data) {
+        int r;
+
+        assert_return(m, -EINVAL);
+        assert_return(!m->sealed, -EPERM);
+
+        r = message_attribute_has_type(m, NULL, attr_type, NETLINK_TYPE_U8);
+        if (r < 0)
+                return r;
+
+        r = add_rtattr(m, attr_type, &data, sizeof(uint8_t));
+        if (r < 0)
+                return r;
+
+        return 0;
+}
+
+int sd_netlink_message_append_u16(sd_netlink_message *m, uint16_t attr_type, uint16_t data) {
+        int r;
+
+        assert_return(m, -EINVAL);
+        assert_return(!m->sealed, -EPERM);
+
+        r = message_attribute_has_type(m, NULL, attr_type, NETLINK_TYPE_U16);
+        if (r < 0)
+                return r;
+
+        r = add_rtattr(m, attr_type, &data, sizeof(uint16_t));
+        if (r < 0)
+                return r;
+
+        return 0;
+}
+
+int sd_netlink_message_append_u32(sd_netlink_message *m, uint16_t attr_type, uint32_t data) {
+        int r;
+
+        assert_return(m, -EINVAL);
+        assert_return(!m->sealed, -EPERM);
+
+        r = message_attribute_has_type(m, NULL, attr_type, NETLINK_TYPE_U32);
+        if (r < 0)
+                return r;
+
+        r = add_rtattr(m, attr_type, &data, sizeof(uint32_t));
+        if (r < 0)
+                return r;
+
+        return 0;
+}
+
+int sd_netlink_message_append_u64(sd_netlink_message *m, uint16_t attr_type, uint64_t data) {
+        int r;
+
+        assert_return(m, -EINVAL);
+        assert_return(!m->sealed, -EPERM);
+
+        r = message_attribute_has_type(m, NULL, attr_type, NETLINK_TYPE_U64);
+        if (r < 0)
+                return r;
+
+        r = add_rtattr(m, attr_type, &data, sizeof(uint64_t));
+        if (r < 0)
+                return r;
+
+        return 0;
+}
+
+int sd_netlink_message_append_s8(sd_netlink_message *m, uint16_t attr_type, int8_t data) {
+        int r;
+
+        assert_return(m, -EINVAL);
+        assert_return(!m->sealed, -EPERM);
+
+        r = message_attribute_has_type(m, NULL, attr_type, NETLINK_TYPE_S8);
+        if (r < 0)
+                return r;
+
+        r = add_rtattr(m, attr_type, &data, sizeof(int8_t));
+        if (r < 0)
+                return r;
+
+        return 0;
+}
+
+int sd_netlink_message_append_s16(sd_netlink_message *m, uint16_t attr_type, int16_t data) {
+        int r;
+
+        assert_return(m, -EINVAL);
+        assert_return(!m->sealed, -EPERM);
+
+        r = message_attribute_has_type(m, NULL, attr_type, NETLINK_TYPE_S16);
+        if (r < 0)
+                return r;
+
+        r = add_rtattr(m, attr_type, &data, sizeof(int16_t));
+        if (r < 0)
+                return r;
+
+        return 0;
+}
+
+int sd_netlink_message_append_s32(sd_netlink_message *m, uint16_t attr_type, int32_t data) {
+        int r;
+
+        assert_return(m, -EINVAL);
+        assert_return(!m->sealed, -EPERM);
+
+        r = message_attribute_has_type(m, NULL, attr_type, NETLINK_TYPE_S32);
+        if (r < 0)
+                return r;
+
+        r = add_rtattr(m, attr_type, &data, sizeof(int32_t));
+        if (r < 0)
+                return r;
+
+        return 0;
+}
+
+int sd_netlink_message_append_s64(sd_netlink_message *m, uint16_t attr_type, int64_t data) {
+        int r;
+
+        assert_return(m, -EINVAL);
+        assert_return(!m->sealed, -EPERM);
+
+        r = message_attribute_has_type(m, NULL, attr_type, NETLINK_TYPE_S64);
+        if (r < 0)
+                return r;
+
+        r = add_rtattr(m, attr_type, &data, sizeof(int64_t));
+        if (r < 0)
+                return r;
+
+        return 0;
+}
+
+int sd_netlink_message_append_data(sd_netlink_message *m, uint16_t attr_type, const void *data, size_t len) {
+        int r;
+
+        assert_return(m, -EINVAL);
+        assert_return(!m->sealed, -EPERM);
+
+        r = add_rtattr(m, attr_type, data, len);
+        if (r < 0)
+                return r;
+
+        return 0;
+}
+
+int sd_netlink_message_append_container_data(
+                sd_netlink_message *m,
+                uint16_t container_type,
+                uint16_t attr_type,
+                const void *data,
+                size_t len) {
+
+        int r;
+
+        assert_return(m, -EINVAL);
+        assert_return(!m->sealed, -EPERM);
+
+        r = sd_netlink_message_open_container(m, container_type);
+        if (r < 0)
+                return r;
+
+        r = sd_netlink_message_append_data(m, attr_type, data, len);
+        if (r < 0)
+                return r;
+
+        return sd_netlink_message_close_container(m);
+}
+
+int netlink_message_append_in_addr_union(sd_netlink_message *m, uint16_t attr_type, int family, const union in_addr_union *data) {
+        int r;
+
+        assert_return(m, -EINVAL);
+        assert_return(!m->sealed, -EPERM);
+        assert_return(data, -EINVAL);
+        assert_return(IN_SET(family, AF_INET, AF_INET6), -EINVAL);
+
+        r = message_attribute_has_type(m, NULL, attr_type, NETLINK_TYPE_IN_ADDR);
+        if (r < 0)
+                return r;
+
+        r = add_rtattr(m, attr_type, data, FAMILY_ADDRESS_SIZE(family));
+        if (r < 0)
+                return r;
+
+        return 0;
+}
+
+int sd_netlink_message_append_in_addr(sd_netlink_message *m, uint16_t attr_type, const struct in_addr *data) {
+        return netlink_message_append_in_addr_union(m, attr_type, AF_INET, (const union in_addr_union *) data);
+}
+
+int sd_netlink_message_append_in6_addr(sd_netlink_message *m, uint16_t attr_type, const struct in6_addr *data) {
+        return netlink_message_append_in_addr_union(m, attr_type, AF_INET6, (const union in_addr_union *) data);
+}
+
+int netlink_message_append_sockaddr_union(sd_netlink_message *m, uint16_t attr_type, const union sockaddr_union *data) {
+        int r;
+
+        assert_return(m, -EINVAL);
+        assert_return(!m->sealed, -EPERM);
+        assert_return(data, -EINVAL);
+        assert_return(IN_SET(data->sa.sa_family, AF_INET, AF_INET6), -EINVAL);
+
+        r = message_attribute_has_type(m, NULL, attr_type, NETLINK_TYPE_SOCKADDR);
+        if (r < 0)
+                return r;
+
+        r = add_rtattr(m, attr_type, data, data->sa.sa_family == AF_INET ? sizeof(struct sockaddr_in) : sizeof(struct sockaddr_in6));
+        if (r < 0)
+                return r;
+
+        return 0;
+}
+
+int sd_netlink_message_append_sockaddr_in(sd_netlink_message *m, uint16_t attr_type, const struct sockaddr_in *data) {
+        return netlink_message_append_sockaddr_union(m, attr_type, (const union sockaddr_union *) data);
+}
+
+int sd_netlink_message_append_sockaddr_in6(sd_netlink_message *m, uint16_t attr_type, const struct sockaddr_in6 *data) {
+        return netlink_message_append_sockaddr_union(m, attr_type, (const union sockaddr_union *) data);
+}
+
+int sd_netlink_message_append_ether_addr(sd_netlink_message *m, uint16_t attr_type, const struct ether_addr *data) {
+        int r;
+
+        assert_return(m, -EINVAL);
+        assert_return(!m->sealed, -EPERM);
+        assert_return(data, -EINVAL);
+
+        r = message_attribute_has_type(m, NULL, attr_type, NETLINK_TYPE_ETHER_ADDR);
+        if (r < 0)
+                return r;
+
+        r = add_rtattr(m, attr_type, data, ETH_ALEN);
+        if (r < 0)
+                return r;
+
+        return 0;
+}
+
+int netlink_message_append_hw_addr(sd_netlink_message *m, uint16_t attr_type, const struct hw_addr_data *data) {
+        int r;
+
+        assert_return(m, -EINVAL);
+        assert_return(!m->sealed, -EPERM);
+        assert_return(data, -EINVAL);
+        assert_return(data->length > 0, -EINVAL);
+
+        r = message_attribute_has_type(m, NULL, attr_type, NETLINK_TYPE_ETHER_ADDR);
+        if (r < 0)
+                return r;
+
+        r = add_rtattr(m, attr_type, data->bytes, data->length);
+        if (r < 0)
+                return r;
+
+        return 0;
+}
+
+int sd_netlink_message_append_cache_info(sd_netlink_message *m, uint16_t attr_type, const struct ifa_cacheinfo *info) {
+        int r;
+
+        assert_return(m, -EINVAL);
+        assert_return(!m->sealed, -EPERM);
+        assert_return(info, -EINVAL);
+
+        r = message_attribute_has_type(m, NULL, attr_type, NETLINK_TYPE_CACHE_INFO);
+        if (r < 0)
+                return r;
+
+        r = add_rtattr(m, attr_type, info, sizeof(struct ifa_cacheinfo));
+        if (r < 0)
+                return r;
+
+        return 0;
+}
+
+int sd_netlink_message_open_container(sd_netlink_message *m, uint16_t attr_type) {
+        size_t size;
+        int r;
+
+        assert_return(m, -EINVAL);
+        assert_return(!m->sealed, -EPERM);
+        /* m->containers[m->n_containers + 1] is accessed both in read and write. Prevent access out of bound */
+        assert_return(m->n_containers < (NETLINK_CONTAINER_DEPTH - 1), -ERANGE);
+
+        r = message_attribute_has_type(m, &size, attr_type, NETLINK_TYPE_NESTED);
+        if (r < 0) {
+                const NLAPolicySetUnion *policy_set_union;
+                int family;
+
+                r = message_attribute_has_type(m, &size, attr_type, NETLINK_TYPE_NESTED_UNION_BY_FAMILY);
+                if (r < 0)
+                        return r;
+
+                r = sd_rtnl_message_get_family(m, &family);
+                if (r < 0)
+                        return r;
+
+                policy_set_union = policy_set_get_policy_set_union(
+                                m->containers[m->n_containers].policy_set,
+                                attr_type);
+                if (!policy_set_union)
+                        return -EOPNOTSUPP;
+
+                m->containers[m->n_containers + 1].policy_set =
+                        policy_set_union_get_policy_set_by_family(
+                                policy_set_union,
+                                family);
+        } else
+                m->containers[m->n_containers + 1].policy_set =
+                        policy_set_get_policy_set(
+                                m->containers[m->n_containers].policy_set,
+                                attr_type);
+        if (!m->containers[m->n_containers + 1].policy_set)
+                return -EOPNOTSUPP;
+
+        r = add_rtattr(m, attr_type | NLA_F_NESTED, NULL, size);
+        if (r < 0)
+                return r;
+
+        m->containers[m->n_containers++].offset = r;
+
+        return 0;
+}
+
+int sd_netlink_message_open_container_union(sd_netlink_message *m, uint16_t attr_type, const char *key) {
+        const NLAPolicySetUnion *policy_set_union;
+        int r;
+
+        assert_return(m, -EINVAL);
+        assert_return(!m->sealed, -EPERM);
+        assert_return(m->n_containers < (NETLINK_CONTAINER_DEPTH - 1), -ERANGE);
+
+        r = message_attribute_has_type(m, NULL, attr_type, NETLINK_TYPE_NESTED_UNION_BY_STRING);
+        if (r < 0)
+                return r;
+
+        policy_set_union = policy_set_get_policy_set_union(
+                        m->containers[m->n_containers].policy_set,
+                        attr_type);
+        if (!policy_set_union)
+                return -EOPNOTSUPP;
+
+        m->containers[m->n_containers + 1].policy_set =
+                policy_set_union_get_policy_set_by_string(
+                        policy_set_union,
+                        key);
+        if (!m->containers[m->n_containers + 1].policy_set)
+                return -EOPNOTSUPP;
+
+        r = sd_netlink_message_append_string(m, policy_set_union_get_match_attribute(policy_set_union), key);
+        if (r < 0)
+                return r;
+
+        /* do we ever need non-null size */
+        r = add_rtattr(m, attr_type | NLA_F_NESTED, NULL, 0);
+        if (r < 0)
+                return r;
+
+        m->containers[m->n_containers++].offset = r;
+
+        return 0;
+}
+
+int sd_netlink_message_close_container(sd_netlink_message *m) {
+        assert_return(m, -EINVAL);
+        assert_return(!m->sealed, -EPERM);
+        assert_return(m->n_containers > 0, -EINVAL);
+
+        m->containers[m->n_containers].policy_set = NULL;
+        m->containers[m->n_containers].offset = 0;
+        m->n_containers--;
+
+        return 0;
+}
+
+int sd_netlink_message_open_array(sd_netlink_message *m, uint16_t attr_type) {
+        int r;
+
+        assert_return(m, -EINVAL);
+        assert_return(!m->sealed, -EPERM);
+        assert_return(m->n_containers < (NETLINK_CONTAINER_DEPTH - 1), -ERANGE);
+
+        r = add_rtattr(m, attr_type | NLA_F_NESTED, NULL, 0);
+        if (r < 0)
+                return r;
+
+        m->containers[m->n_containers].offset = r;
+        m->n_containers++;
+        m->containers[m->n_containers].policy_set = m->containers[m->n_containers - 1].policy_set;
+
+        return 0;
+}
+
+int sd_netlink_message_cancel_array(sd_netlink_message *m) {
+        uint32_t rta_len;
+
+        assert_return(m, -EINVAL);
+        assert_return(!m->sealed, -EPERM);
+        assert_return(m->n_containers > 1, -EINVAL);
+
+        rta_len = GET_CONTAINER(m, (m->n_containers - 1))->rta_len;
+
+        for (unsigned i = 0; i < m->n_containers; i++)
+                GET_CONTAINER(m, i)->rta_len -= rta_len;
+
+        m->hdr->nlmsg_len -= rta_len;
+
+        m->n_containers--;
+        m->containers[m->n_containers].policy_set = NULL;
+
+        return 0;
+}
+
+static int netlink_message_read_internal(
+                sd_netlink_message *m,
+                uint16_t attr_type,
+                void **ret_data,
+                bool *ret_net_byteorder) {
+
+        struct netlink_attribute *attribute;
+        struct rtattr *rta;
+
+        assert_return(m, -EINVAL);
+        assert_return(m->sealed, -EPERM);
+
+        assert(m->n_containers < NETLINK_CONTAINER_DEPTH);
+
+        if (!m->containers[m->n_containers].attributes)
+                return -ENODATA;
+
+        if (attr_type > m->containers[m->n_containers].max_attribute)
+                return -ENODATA;
+
+        attribute = &m->containers[m->n_containers].attributes[attr_type];
+
+        if (attribute->offset == 0)
+                return -ENODATA;
+
+        rta = (struct rtattr*)((uint8_t *) m->hdr + attribute->offset);
+
+        if (ret_data)
+                *ret_data = RTA_DATA(rta);
+
+        if (ret_net_byteorder)
+                *ret_net_byteorder = attribute->net_byteorder;
+
+        return RTA_PAYLOAD(rta);
+}
+
+int sd_netlink_message_read(sd_netlink_message *m, uint16_t attr_type, size_t size, void *data) {
+        void *attr_data;
+        int r;
+
+        assert_return(m, -EINVAL);
+
+        r = netlink_message_read_internal(m, attr_type, &attr_data, NULL);
+        if (r < 0)
+                return r;
+
+        if ((size_t) r > size)
+                return -ENOBUFS;
+
+        if (data)
+                memcpy(data, attr_data, r);
+
+        return r;
+}
+
+int sd_netlink_message_read_data(sd_netlink_message *m, uint16_t attr_type, size_t *ret_size, void **ret_data) {
+        void *attr_data;
+        int r;
+
+        assert_return(m, -EINVAL);
+
+        r = netlink_message_read_internal(m, attr_type, &attr_data, NULL);
+        if (r < 0)
+                return r;
+
+        if (ret_data) {
+                void *data;
+
+                data = memdup(attr_data, r);
+                if (!data)
+                        return -ENOMEM;
+
+                *ret_data = data;
+        }
+
+        if (ret_size)
+                *ret_size = r;
+
+        return r;
+}
+
+int sd_netlink_message_read_data_suffix0(sd_netlink_message *m, uint16_t attr_type, size_t *ret_size, void **ret_data) {
+        void *attr_data;
+        int r;
+
+        assert_return(m, -EINVAL);
+
+        r = netlink_message_read_internal(m, attr_type, &attr_data, NULL);
+        if (r < 0)
+                return r;
+
+        if (ret_data) {
+                void *data;
+
+                data = memdup_suffix0(attr_data, r);
+                if (!data)
+                        return -ENOMEM;
+
+                *ret_data = data;
+        }
+
+        if (ret_size)
+                *ret_size = r;
+
+        return r;
+}
+
+int sd_netlink_message_read_string_strdup(sd_netlink_message *m, uint16_t attr_type, char **data) {
+        void *attr_data;
+        int r;
+
+        assert_return(m, -EINVAL);
+
+        r = message_attribute_has_type(m, NULL, attr_type, NETLINK_TYPE_STRING);
+        if (r < 0)
+                return r;
+
+        r = netlink_message_read_internal(m, attr_type, &attr_data, NULL);
+        if (r < 0)
+                return r;
+
+        if (data) {
+                char *str;
+
+                str = strndup(attr_data, r);
+                if (!str)
+                        return -ENOMEM;
+
+                *data = str;
+        }
+
+        return 0;
+}
+
+int sd_netlink_message_read_string(sd_netlink_message *m, uint16_t attr_type, const char **data) {
+        void *attr_data;
+        int r;
+
+        assert_return(m, -EINVAL);
+
+        r = message_attribute_has_type(m, NULL, attr_type, NETLINK_TYPE_STRING);
+        if (r < 0)
+                return r;
+
+        r = netlink_message_read_internal(m, attr_type, &attr_data, NULL);
+        if (r < 0)
+                return r;
+
+        if (strnlen(attr_data, r) >= (size_t) r)
+                return -EIO;
+
+        if (data)
+                *data = (const char *) attr_data;
+
+        return 0;
+}
+
+int sd_netlink_message_read_u8(sd_netlink_message *m, uint16_t attr_type, uint8_t *data) {
+        void *attr_data;
+        int r;
+
+        assert_return(m, -EINVAL);
+
+        r = message_attribute_has_type(m, NULL, attr_type, NETLINK_TYPE_U8);
+        if (r < 0)
+                return r;
+
+        r = netlink_message_read_internal(m, attr_type, &attr_data, NULL);
+        if (r < 0)
+                return r;
+
+        if ((size_t) r < sizeof(uint8_t))
+                return -EIO;
+
+        if (data)
+                *data = *(uint8_t *) attr_data;
+
+        return 0;
+}
+
+int sd_netlink_message_read_u16(sd_netlink_message *m, uint16_t attr_type, uint16_t *data) {
+        void *attr_data;
+        bool net_byteorder;
+        int r;
+
+        assert_return(m, -EINVAL);
+
+        r = message_attribute_has_type(m, NULL, attr_type, NETLINK_TYPE_U16);
+        if (r < 0)
+                return r;
+
+        r = netlink_message_read_internal(m, attr_type, &attr_data, &net_byteorder);
+        if (r < 0)
+                return r;
+
+        if ((size_t) r < sizeof(uint16_t))
+                return -EIO;
+
+        if (data) {
+                if (net_byteorder)
+                        *data = be16toh(*(uint16_t *) attr_data);
+                else
+                        *data = *(uint16_t *) attr_data;
+        }
+
+        return 0;
+}
+
+int sd_netlink_message_read_u32(sd_netlink_message *m, uint16_t attr_type, uint32_t *data) {
+        void *attr_data;
+        bool net_byteorder;
+        int r;
+
+        assert_return(m, -EINVAL);
+
+        r = message_attribute_has_type(m, NULL, attr_type, NETLINK_TYPE_U32);
+        if (r < 0)
+                return r;
+
+        r = netlink_message_read_internal(m, attr_type, &attr_data, &net_byteorder);
+        if (r < 0)
+                return r;
+
+        if ((size_t) r < sizeof(uint32_t))
+                return -EIO;
+
+        if (data) {
+                if (net_byteorder)
+                        *data = be32toh(*(uint32_t *) attr_data);
+                else
+                        *data = *(uint32_t *) attr_data;
+        }
+
+        return 0;
+}
+
+int sd_netlink_message_read_ether_addr(sd_netlink_message *m, uint16_t attr_type, struct ether_addr *data) {
+        void *attr_data;
+        int r;
+
+        assert_return(m, -EINVAL);
+
+        r = message_attribute_has_type(m, NULL, attr_type, NETLINK_TYPE_ETHER_ADDR);
+        if (r < 0)
+                return r;
+
+        r = netlink_message_read_internal(m, attr_type, &attr_data, NULL);
+        if (r < 0)
+                return r;
+
+        if ((size_t) r < sizeof(struct ether_addr))
+                return -EIO;
+
+        if (data)
+                memcpy(data, attr_data, sizeof(struct ether_addr));
+
+        return 0;
+}
+
+int netlink_message_read_hw_addr(sd_netlink_message *m, uint16_t attr_type, struct hw_addr_data *data) {
+        void *attr_data;
+        int r;
+
+        assert_return(m, -EINVAL);
+
+        r = message_attribute_has_type(m, NULL, attr_type, NETLINK_TYPE_ETHER_ADDR);
+        if (r < 0)
+                return r;
+
+        r = netlink_message_read_internal(m, attr_type, &attr_data, NULL);
+        if (r < 0)
+                return r;
+
+        if (r > HW_ADDR_MAX_SIZE)
+                return -EIO;
+
+        if (data) {
+                memcpy(data->bytes, attr_data, r);
+                data->length = r;
+        }
+
+        return 0;
+}
+
+int sd_netlink_message_read_cache_info(sd_netlink_message *m, uint16_t attr_type, struct ifa_cacheinfo *info) {
+        void *attr_data;
+        int r;
+
+        assert_return(m, -EINVAL);
+
+        r = message_attribute_has_type(m, NULL, attr_type, NETLINK_TYPE_CACHE_INFO);
+        if (r < 0)
+                return r;
+
+        r = netlink_message_read_internal(m, attr_type, &attr_data, NULL);
+        if (r < 0)
+                return r;
+
+        if ((size_t) r < sizeof(struct ifa_cacheinfo))
+                return -EIO;
+
+        if (info)
+                memcpy(info, attr_data, sizeof(struct ifa_cacheinfo));
+
+        return 0;
+}
+
+int netlink_message_read_in_addr_union(sd_netlink_message *m, uint16_t attr_type, int family, union in_addr_union *data) {
+        void *attr_data;
+        int r;
+
+        assert_return(m, -EINVAL);
+        assert_return(IN_SET(family, AF_INET, AF_INET6), -EINVAL);
+
+        r = message_attribute_has_type(m, NULL, attr_type, NETLINK_TYPE_IN_ADDR);
+        if (r < 0)
+                return r;
+
+        r = netlink_message_read_internal(m, attr_type, &attr_data, NULL);
+        if (r < 0)
+                return r;
+
+        if ((size_t) r < FAMILY_ADDRESS_SIZE(family))
+                return -EIO;
+
+        if (data)
+                memcpy(data, attr_data, FAMILY_ADDRESS_SIZE(family));
+
+        return 0;
+}
+
+int sd_netlink_message_read_in_addr(sd_netlink_message *m, uint16_t attr_type, struct in_addr *data) {
+        union in_addr_union u;
+        int r;
+
+        r = netlink_message_read_in_addr_union(m, attr_type, AF_INET, &u);
+        if (r >= 0 && data)
+                *data = u.in;
+
+        return r;
+}
+
+int sd_netlink_message_read_in6_addr(sd_netlink_message *m, uint16_t attr_type, struct in6_addr *data) {
+        union in_addr_union u;
+        int r;
+
+        r = netlink_message_read_in_addr_union(m, attr_type, AF_INET6, &u);
+        if (r >= 0 && data)
+                *data = u.in6;
+
+        return r;
+}
+
+int sd_netlink_message_has_flag(sd_netlink_message *m, uint16_t attr_type) {
+        void *attr_data;
+        int r;
+
+        assert_return(m, -EINVAL);
+
+        /* This returns 1 when the flag is set, 0 when not set, negative errno on error. */
+
+        r = message_attribute_has_type(m, NULL, attr_type, NETLINK_TYPE_FLAG);
+        if (r < 0)
+                return r;
+
+        r = netlink_message_read_internal(m, attr_type, &attr_data, NULL);
+        if (r == -ENODATA)
+                return 0;
+        if (r < 0)
+                return r;
+
+        return 1;
+}
+
+int sd_netlink_message_read_strv(sd_netlink_message *m, uint16_t container_type, uint16_t attr_type, char ***ret) {
+        _cleanup_strv_free_ char **s = NULL;
+        const NLAPolicySet *policy_set;
+        const NLAPolicy *policy;
+        struct rtattr *rta;
+        void *container;
+        size_t rt_len;
+        int r;
+
+        assert_return(m, -EINVAL);
+        assert_return(m->n_containers < NETLINK_CONTAINER_DEPTH, -EINVAL);
+
+        policy = policy_set_get_policy(
+                        m->containers[m->n_containers].policy_set,
+                        container_type);
+        if (!policy)
+                return -EOPNOTSUPP;
+
+        if (policy_get_type(policy) != NETLINK_TYPE_NESTED)
+                return -EINVAL;
+
+        policy_set = policy_set_get_policy_set(
+                        m->containers[m->n_containers].policy_set,
+                        container_type);
+        if (!policy_set)
+                return -EOPNOTSUPP;
+
+        policy = policy_set_get_policy(policy_set, attr_type);
+        if (!policy)
+                return -EOPNOTSUPP;
+
+        if (policy_get_type(policy) != NETLINK_TYPE_STRING)
+                return -EINVAL;
+
+        r = netlink_message_read_internal(m, container_type, &container, NULL);
+        if (r < 0)
+                return r;
+
+        rt_len = (size_t) r;
+        rta = container;
+
+        /* RTA_OK() macro compares with rta->rt_len, which is unsigned short, and
+         * LGTM.com analysis does not like the type difference. Hence, here we
+         * introduce an unsigned short variable as a workaround. */
+        unsigned short len = rt_len;
+        for (; RTA_OK(rta, len); rta = RTA_NEXT(rta, len)) {
+                uint16_t type;
+
+                type = RTA_TYPE(rta);
+                if (type != attr_type)
+                        continue;
+
+                r = strv_extend(&s, RTA_DATA(rta));
+                if (r < 0)
+                        return r;
+        }
+
+        *ret = TAKE_PTR(s);
+        return 0;
+}
+
+static int netlink_container_parse(
+                sd_netlink_message *m,
+                struct netlink_container *container,
+                struct rtattr *rta,
+                size_t rt_len) {
+
+        _cleanup_free_ struct netlink_attribute *attributes = NULL;
+        uint16_t max_attr = 0;
+
+        /* RTA_OK() macro compares with rta->rt_len, which is unsigned short, and
+         * LGTM.com analysis does not like the type difference. Hence, here we
+         * introduce an unsigned short variable as a workaround. */
+        unsigned short len = rt_len;
+        for (; RTA_OK(rta, len); rta = RTA_NEXT(rta, len)) {
+                uint16_t attr;
+
+                attr = RTA_TYPE(rta);
+                max_attr = MAX(max_attr, attr);
+
+                if (!GREEDY_REALLOC0(attributes, (size_t) max_attr + 1))
+                        return -ENOMEM;
+
+                if (attributes[attr].offset != 0)
+                        log_debug("sd-netlink: message parse - overwriting repeated attribute");
+
+                attributes[attr].offset = (uint8_t *) rta - (uint8_t *) m->hdr;
+                attributes[attr].nested = RTA_FLAGS(rta) & NLA_F_NESTED;
+                attributes[attr].net_byteorder = RTA_FLAGS(rta) & NLA_F_NET_BYTEORDER;
+        }
+
+        container->attributes = TAKE_PTR(attributes);
+        container->max_attribute = max_attr;
+
+        return 0;
+}
+
+int sd_netlink_message_enter_container(sd_netlink_message *m, uint16_t attr_type) {
+        const NLAPolicy *policy;
+        const NLAPolicySet *policy_set;
+        void *container;
+        size_t size;
+        int r;
+
+        assert_return(m, -EINVAL);
+        assert_return(m->n_containers < (NETLINK_CONTAINER_DEPTH - 1), -EINVAL);
+
+        policy = policy_set_get_policy(
+                        m->containers[m->n_containers].policy_set,
+                        attr_type);
+        if (!policy)
+                return -EOPNOTSUPP;
+
+        switch (policy_get_type(policy)) {
+        case NETLINK_TYPE_NESTED:
+                policy_set = policy_set_get_policy_set(
+                                m->containers[m->n_containers].policy_set,
+                                attr_type);
+                break;
+
+        case NETLINK_TYPE_NESTED_UNION_BY_STRING: {
+                const NLAPolicySetUnion *policy_set_union;
+                const char *key;
+
+                policy_set_union = policy_get_policy_set_union(policy);
+                if (!policy_set_union)
+                        return -EOPNOTSUPP;
+
+                r = sd_netlink_message_read_string(
+                                m,
+                                policy_set_union_get_match_attribute(policy_set_union),
+                                &key);
+                if (r < 0)
+                        return r;
+
+                policy_set = policy_set_union_get_policy_set_by_string(
+                                policy_set_union,
+                                key);
+                break;
+        }
+        case NETLINK_TYPE_NESTED_UNION_BY_FAMILY: {
+                const NLAPolicySetUnion *policy_set_union;
+                int family;
+
+                policy_set_union = policy_get_policy_set_union(policy);
+                if (!policy_set_union)
+                        return -EOPNOTSUPP;
+
+                r = sd_rtnl_message_get_family(m, &family);
+                if (r < 0)
+                        return r;
+
+                policy_set = policy_set_union_get_policy_set_by_family(
+                                policy_set_union,
+                                family);
+                break;
+        }
+        default:
+                assert_not_reached();
+        }
+        if (!policy_set)
+                return -EOPNOTSUPP;
+
+        r = netlink_message_read_internal(m, attr_type, &container, NULL);
+        if (r < 0)
+                return r;
+
+        size = (size_t) r;
+        m->n_containers++;
+
+        r = netlink_container_parse(m,
+                                    &m->containers[m->n_containers],
+                                    container,
+                                    size);
+        if (r < 0) {
+                m->n_containers--;
+                return r;
+        }
+
+        m->containers[m->n_containers].policy_set = policy_set;
+
+        return 0;
+}
+
+int sd_netlink_message_enter_array(sd_netlink_message *m, uint16_t attr_type) {
+        void *container;
+        size_t size;
+        int r;
+
+        assert_return(m, -EINVAL);
+        assert_return(m->n_containers < (NETLINK_CONTAINER_DEPTH - 1), -EINVAL);
+
+        r = netlink_message_read_internal(m, attr_type, &container, NULL);
+        if (r < 0)
+                return r;
+
+        size = (size_t) r;
+        m->n_containers++;
+
+        r = netlink_container_parse(m,
+                                    &m->containers[m->n_containers],
+                                    container,
+                                    size);
+        if (r < 0) {
+                m->n_containers--;
+                return r;
+        }
+
+        m->containers[m->n_containers].policy_set = m->containers[m->n_containers - 1].policy_set;
+
+        return 0;
+}
+
+int sd_netlink_message_exit_container(sd_netlink_message *m) {
+        assert_return(m, -EINVAL);
+        assert_return(m->sealed, -EINVAL);
+        assert_return(m->n_containers > 0, -EINVAL);
+
+        m->containers[m->n_containers].attributes = mfree(m->containers[m->n_containers].attributes);
+        m->containers[m->n_containers].max_attribute = 0;
+        m->containers[m->n_containers].policy_set = NULL;
+
+        m->n_containers--;
+
+        return 0;
+}
+
+int sd_netlink_message_get_max_attribute(sd_netlink_message *m, uint16_t *ret) {
+        assert_return(m, -EINVAL);
+        assert_return(m->sealed, -EINVAL);
+        assert_return(ret, -EINVAL);
+
+        *ret = m->containers[m->n_containers].max_attribute;
+        return 0;
+}
+
+int sd_netlink_message_is_error(sd_netlink_message *m) {
+        assert_return(m, 0);
+        assert_return(m->hdr, 0);
+
+        return m->hdr->nlmsg_type == NLMSG_ERROR;
+}
+
+int sd_netlink_message_get_errno(sd_netlink_message *m) {
+        struct nlmsgerr *err;
+
+        assert_return(m, -EINVAL);
+        assert_return(m->hdr, -EINVAL);
+
+        if (!sd_netlink_message_is_error(m))
+                return 0;
+
+        err = NLMSG_DATA(m->hdr);
+
+        return err->error;
+}
+
+static int netlink_message_parse_error(sd_netlink_message *m) {
+        struct nlmsgerr *err = NLMSG_DATA(m->hdr);
+        size_t hlen = sizeof(struct nlmsgerr);
+
+        /* no TLVs, nothing to do here */
+        if (!(m->hdr->nlmsg_flags & NLM_F_ACK_TLVS))
+                return 0;
+
+        /* if NLM_F_CAPPED is set then the inner err msg was capped */
+        if (!(m->hdr->nlmsg_flags & NLM_F_CAPPED))
+                hlen += err->msg.nlmsg_len - sizeof(struct nlmsghdr);
+
+        if (m->hdr->nlmsg_len <= NLMSG_SPACE(hlen))
+                return 0;
+
+        return netlink_container_parse(m,
+                                       &m->containers[m->n_containers],
+                                       (struct rtattr*)((uint8_t*) NLMSG_DATA(m->hdr) + hlen),
+                                       NLMSG_PAYLOAD(m->hdr, hlen));
+}
+
+int sd_netlink_message_rewind(sd_netlink_message *m, sd_netlink *nl) {
+        size_t size;
+        int r;
+
+        assert_return(m, -EINVAL);
+        assert_return(nl, -EINVAL);
+
+        /* don't allow appending to message once parsed */
+        message_seal(m);
+
+        for (unsigned i = 1; i <= m->n_containers; i++)
+                m->containers[i].attributes = mfree(m->containers[i].attributes);
+
+        m->n_containers = 0;
+
+        if (m->containers[0].attributes)
+                /* top-level attributes have already been parsed */
+                return 0;
+
+        assert(m->hdr);
+
+        r = netlink_get_policy_set_and_header_size(nl, m->hdr->nlmsg_type,
+                                                   &m->containers[0].policy_set, &size);
+        if (r < 0)
+                return r;
+
+        if (sd_netlink_message_is_error(m))
+                return netlink_message_parse_error(m);
+
+        return netlink_container_parse(m,
+                                       &m->containers[0],
+                                       (struct rtattr*)((uint8_t*) NLMSG_DATA(m->hdr) + NLMSG_ALIGN(size)),
+                                       NLMSG_PAYLOAD(m->hdr, size));
+}
+
+void message_seal(sd_netlink_message *m) {
+        assert(m);
+
+        m->sealed = true;
+}
+
+sd_netlink_message *sd_netlink_message_next(sd_netlink_message *m) {
+        assert_return(m, NULL);
+
+        return m->next;
+}