libsystemd: split up into subdirs

We still only produce on .so, but let's keep the sources separate to make things a bit
less messy.

1 files changed, 887 insertions, 0 deletions

diff --git a/src/libsystemd/sd-rtnl/rtnl-message.c b/src/libsystemd/sd-rtnl/rtnl-message.c
new file mode 100644
index 0000000000..984115c3c0
--- /dev/null
+++ b/src/libsystemd/sd-rtnl/rtnl-message.c
@@ -0,0 +1,887 @@
+/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
+
+/***
+  This file is part of systemd.
+
+  Copyright 2013 Tom Gundersen <teg@jklm.no>
+
+  systemd is free software; you can redistribute it and/or modify it
+  under the terms of the GNU Lesser General Public License as published by
+  the Free Software Foundation; either version 2.1 of the License, or
+  (at your option) any later version.
+
+  systemd is distributed in the hope that it will be useful, but
+  WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+  Lesser General Public License for more details.
+
+  You should have received a copy of the GNU Lesser General Public License
+  along with systemd; If not, see <http://www.gnu.org/licenses/>.
+***/
+
+#include <linux/rtnetlink.h>
+#include <netinet/in.h>
+#include <netinet/ether.h>
+#include <stdbool.h>
+#include <unistd.h>
+
+#include "util.h"
+#include "refcnt.h"
+
+#include "sd-rtnl.h"
+#include "rtnl-internal.h"
+
+struct sd_rtnl_message {
+        RefCount n_ref;
+
+        struct nlmsghdr *hdr;
+        size_t container_offset; /* offset from hdr to container start */
+        size_t next_rta_offset; /* offset from hdr to next rta */
+
+        bool sealed:1;
+};
+
+#define CURRENT_CONTAINER(m) ((m)->container_offset ? (struct rtattr*)((uint8_t*)(m)->hdr + (m)->container_offset) : NULL)
+#define NEXT_RTA(m) ((struct rtattr*)((uint8_t*)(m)->hdr + (m)->next_rta_offset))
+#define UPDATE_RTA(m, new) (m)->next_rta_offset = (uint8_t*)(new) - (uint8_t*)(m)->hdr;
+
+static int message_new(sd_rtnl_message **ret, size_t initial_size) {
+        sd_rtnl_message *m;
+
+        assert_return(ret, -EINVAL);
+        assert_return(initial_size >= sizeof(struct nlmsghdr), -EINVAL);
+
+        m = new0(sd_rtnl_message, 1);
+        if (!m)
+                return -ENOMEM;
+
+        m->hdr = malloc0(initial_size);
+        if (!m->hdr) {
+                free(m);
+                return -ENOMEM;
+        }
+
+        m->n_ref = REFCNT_INIT;
+
+        m->hdr->nlmsg_flags = NLM_F_REQUEST | NLM_F_ACK;
+        m->sealed = false;
+
+        *ret = m;
+
+        return 0;
+}
+
+int message_new_synthetic_error(int error, uint32_t serial, sd_rtnl_message **ret) {
+        struct nlmsgerr *err;
+        int r;
+
+        assert(error <= 0);
+
+        r = message_new(ret, NLMSG_SPACE(sizeof(struct nlmsgerr)));
+        if (r < 0)
+                return r;
+
+        (*ret)->hdr->nlmsg_len = NLMSG_LENGTH(sizeof(struct nlmsgerr));
+        (*ret)->hdr->nlmsg_type = NLMSG_ERROR;
+        (*ret)->hdr->nlmsg_seq = serial;
+
+        err = NLMSG_DATA((*ret)->hdr);
+
+        err->error = error;
+
+        return 0;
+}
+
+bool message_type_is_route(uint16_t type) {
+        switch (type) {
+                case RTM_NEWROUTE:
+                case RTM_GETROUTE:
+                case RTM_DELROUTE:
+                        return true;
+                default:
+                        return false;
+        }
+}
+
+bool message_type_is_link(uint16_t type) {
+        switch (type) {
+                case RTM_NEWLINK:
+                case RTM_SETLINK:
+                case RTM_GETLINK:
+                case RTM_DELLINK:
+                        return true;
+                default:
+                        return false;
+        }
+}
+
+bool message_type_is_addr(uint16_t type) {
+        switch (type) {
+                case RTM_NEWADDR:
+                case RTM_GETADDR:
+                case RTM_DELADDR:
+                        return true;
+                default:
+                        return false;
+        }
+}
+
+int sd_rtnl_message_route_set_dst_prefixlen(sd_rtnl_message *m, unsigned char prefixlen) {
+        struct rtmsg *rtm;
+
+        rtm = NLMSG_DATA(m->hdr);
+
+        rtm->rtm_dst_len = prefixlen;
+
+        return 0;
+}
+
+int sd_rtnl_message_route_new(uint16_t nlmsg_type, unsigned char rtm_family,
+                              sd_rtnl_message **ret) {
+        struct rtmsg *rtm;
+        int r;
+
+        assert_return(message_type_is_route(nlmsg_type), -EINVAL);
+        assert_return(rtm_family == AF_INET || rtm_family == AF_INET6, -EINVAL);
+        assert_return(ret, -EINVAL);
+
+        r = message_new(ret, NLMSG_SPACE(sizeof(struct rtmsg)));
+        if (r < 0)
+                return r;
+
+        (*ret)->hdr->nlmsg_len = NLMSG_LENGTH(sizeof(struct rtmsg));
+        (*ret)->hdr->nlmsg_type = nlmsg_type;
+        if (nlmsg_type == RTM_NEWROUTE)
+                (*ret)->hdr->nlmsg_flags |= NLM_F_CREATE | NLM_F_EXCL;
+
+        rtm = NLMSG_DATA((*ret)->hdr);
+
+        UPDATE_RTA(*ret, RTM_RTA(rtm));
+
+        rtm->rtm_family = rtm_family;
+        rtm->rtm_scope = RT_SCOPE_UNIVERSE;
+        rtm->rtm_type = RTN_UNICAST;
+        rtm->rtm_table = RT_TABLE_MAIN;
+        rtm->rtm_protocol = RTPROT_BOOT;
+
+        return 0;
+}
+
+int sd_rtnl_message_link_set_flags(sd_rtnl_message *m, unsigned flags) {
+        struct ifinfomsg *ifi;
+
+        ifi = NLMSG_DATA(m->hdr);
+
+        ifi->ifi_flags = flags;
+        ifi->ifi_change = 0xffffffff;
+
+        return 0;
+}
+
+int sd_rtnl_message_link_set_type(sd_rtnl_message *m, unsigned type) {
+        struct ifinfomsg *ifi;
+
+        ifi = NLMSG_DATA(m->hdr);
+
+        ifi->ifi_type = type;
+
+        return 0;
+}
+
+int sd_rtnl_message_link_new(uint16_t nlmsg_type, int index, sd_rtnl_message **ret) {
+        struct ifinfomsg *ifi;
+        int r;
+
+        assert_return(message_type_is_link(nlmsg_type), -EINVAL);
+        assert_return(nlmsg_type == RTM_NEWLINK || index > 0, -EINVAL);
+        assert_return(ret, -EINVAL);
+
+        r = message_new(ret, NLMSG_SPACE(sizeof(struct ifinfomsg)));
+        if (r < 0)
+                return r;
+
+        (*ret)->hdr->nlmsg_len = NLMSG_LENGTH(sizeof(struct ifinfomsg));
+        (*ret)->hdr->nlmsg_type = nlmsg_type;
+        if (nlmsg_type == RTM_NEWLINK)
+                (*ret)->hdr->nlmsg_flags |= NLM_F_CREATE;
+
+        ifi = NLMSG_DATA((*ret)->hdr);
+
+        ifi->ifi_family = AF_UNSPEC;
+        ifi->ifi_index = index;
+
+        UPDATE_RTA(*ret, IFLA_RTA(ifi));
+
+        return 0;
+}
+
+int sd_rtnl_message_addr_new(uint16_t nlmsg_type, int index, unsigned char family, unsigned char prefixlen, unsigned char flags, unsigned char scope, sd_rtnl_message **ret) {
+        struct ifaddrmsg *ifa;
+        int r;
+
+        assert_return(message_type_is_addr(nlmsg_type), -EINVAL);
+        assert_return(index > 0, -EINVAL);
+        assert_return(ret, -EINVAL);
+
+        r = message_new(ret, NLMSG_SPACE(sizeof(struct ifaddrmsg)));
+        if (r < 0)
+                return r;
+
+        (*ret)->hdr->nlmsg_len = NLMSG_LENGTH(sizeof(struct ifaddrmsg));
+        (*ret)->hdr->nlmsg_type = nlmsg_type;
+
+        ifa = NLMSG_DATA((*ret)->hdr);
+
+        ifa->ifa_family = family;
+        ifa->ifa_prefixlen = prefixlen;
+        ifa->ifa_flags = flags;
+        ifa->ifa_scope = scope;
+        ifa->ifa_index = index;
+
+        UPDATE_RTA(*ret, IFA_RTA(ifa));
+
+        return 0;
+}
+
+sd_rtnl_message *sd_rtnl_message_ref(sd_rtnl_message *m) {
+        if (m)
+                assert_se(REFCNT_INC(m->n_ref) >= 2);
+
+        return m;
+}
+
+sd_rtnl_message *sd_rtnl_message_unref(sd_rtnl_message *m) {
+        if (m && REFCNT_DEC(m->n_ref) <= 0) {
+                free(m->hdr);
+                free(m);
+        }
+
+        return NULL;
+}
+
+int sd_rtnl_message_get_type(sd_rtnl_message *m, uint16_t *type) {
+        assert_return(m, -EINVAL);
+        assert_return(type, -EINVAL);
+
+        *type = m->hdr->nlmsg_type;
+
+        return 0;
+}
+
+int sd_rtnl_message_link_get_ifindex(sd_rtnl_message *m, int *ifindex) {
+        struct ifinfomsg *ifi;
+
+        assert_return(m, -EINVAL);
+        assert_return(m->hdr, -EINVAL);
+        assert_return(message_type_is_link(m->hdr->nlmsg_type), -EINVAL);
+        assert_return(ifindex, -EINVAL);
+
+        ifi = NLMSG_DATA(m->hdr);
+
+        *ifindex = ifi->ifi_index;
+
+        return 0;
+}
+
+int sd_rtnl_message_link_get_flags(sd_rtnl_message *m, unsigned *flags) {
+        struct ifinfomsg *ifi;
+
+        assert_return(m, -EINVAL);
+        assert_return(m->hdr, -EINVAL);
+        assert_return(message_type_is_link(m->hdr->nlmsg_type), -EINVAL);
+        assert_return(flags, -EINVAL);
+
+        ifi = NLMSG_DATA(m->hdr);
+
+        *flags = ifi->ifi_flags;
+
+        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) {
+        uint32_t rta_length, message_length;
+        struct nlmsghdr *new_hdr;
+        struct rtattr *rta;
+        char *padding;
+
+        assert(m);
+        assert(m->hdr);
+        assert(NLMSG_ALIGN(m->hdr->nlmsg_len) == m->hdr->nlmsg_len);
+        assert(!data || data_length > 0);
+
+        /* get the size of the new rta attribute (with padding at the end) */
+        rta_length = RTA_LENGTH(data_length);
+
+        /* get the new message size (with padding at the end) */
+        message_length = m->hdr->nlmsg_len + RTA_ALIGN(rta_length);
+
+        /* 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);
+
+        /* if we are inside a container, extend it */
+        if (CURRENT_CONTAINER(m))
+                CURRENT_CONTAINER(m)->rta_len += message_length - m->hdr->nlmsg_len;
+
+        /* fill in the attribute */
+        rta->rta_type = type;
+        rta->rta_len = rta_length;
+        if (!data) {
+                /* this is the start of a new container */
+                m->container_offset = m->hdr->nlmsg_len;
+        } else {
+                /* we don't deal with the case where the user lies about the type
+                 * and gives us too little data (so don't do that)
+                */
+                padding = mempcpy(RTA_DATA(rta), data, data_length);
+                /* make sure also the padding at the end of the message is initialized */
+                memzero(padding,
+                        (uint8_t *) m->hdr + message_length - (uint8_t *) padding);
+        }
+
+        /* update message size */
+        m->hdr->nlmsg_len = message_length;
+
+        return 0;
+}
+
+int sd_rtnl_message_append_string(sd_rtnl_message *m, unsigned short type, const char *data) {
+        uint16_t rtm_type;
+        int r;
+
+        assert_return(m, -EINVAL);
+        assert_return(data, -EINVAL);
+
+        r = sd_rtnl_message_get_type(m, &rtm_type);
+        if (r < 0)
+                return r;
+
+        /* check that the type is correct */
+        switch (rtm_type) {
+                case RTM_NEWLINK:
+                case RTM_SETLINK:
+                case RTM_GETLINK:
+                case RTM_DELLINK:
+                        if (CURRENT_CONTAINER(m)) {
+                                if (CURRENT_CONTAINER(m)->rta_type != IFLA_LINKINFO ||
+                                    type != IFLA_INFO_KIND)
+                                        return -ENOTSUP;
+                        } else {
+                                switch (type) {
+                                        case IFLA_IFNAME:
+                                        case IFLA_IFALIAS:
+                                        case IFLA_QDISC:
+                                                break;
+                                        default:
+                                                return -ENOTSUP;
+                                }
+                        }
+                        break;
+                case RTM_NEWADDR:
+                case RTM_GETADDR:
+                case RTM_DELADDR:
+                        if (type != IFA_LABEL)
+                                return -ENOTSUP;
+                        break;
+                default:
+                        return -ENOTSUP;
+        }
+
+        r = add_rtattr(m, type, data, strlen(data) + 1);
+        if (r < 0)
+                return r;
+
+        return 0;
+}
+
+int sd_rtnl_message_append_u32(sd_rtnl_message *m, unsigned short type, uint32_t data) {
+        uint16_t rtm_type;
+        int r;
+
+        assert_return(m, -EINVAL);
+
+        r = sd_rtnl_message_get_type(m, &rtm_type);
+        if (r < 0)
+                return r;
+
+        /* check that the type is correct */
+        switch (rtm_type) {
+                case RTM_NEWLINK:
+                case RTM_SETLINK:
+                case RTM_GETLINK:
+                case RTM_DELLINK:
+                        switch (type) {
+                                case IFLA_MASTER:
+                                case IFLA_MTU:
+                                case IFLA_LINK:
+                                        break;
+                                default:
+                                        return -ENOTSUP;
+                        }
+                        break;
+                case RTM_NEWROUTE:
+                case RTM_GETROUTE:
+                case RTM_DELROUTE:
+                        switch (type) {
+                                case RTA_TABLE:
+                                case RTA_PRIORITY:
+                                case RTA_IIF:
+                                case RTA_OIF:
+                                        break;
+                                default:
+                                        return -ENOTSUP;
+                        }
+                        break;
+                default:
+                        return -ENOTSUP;
+        }
+
+        r = add_rtattr(m, type, &data, sizeof(uint32_t));
+        if (r < 0)
+                return r;
+
+        return 0;
+}
+
+int sd_rtnl_message_append_in_addr(sd_rtnl_message *m, unsigned short type, const struct in_addr *data) {
+        struct ifaddrmsg *ifa;
+        struct rtmsg *rtm;
+        uint16_t rtm_type;
+        int r;
+
+        assert_return(m, -EINVAL);
+        assert_return(data, -EINVAL);
+
+        r = sd_rtnl_message_get_type(m, &rtm_type);
+        if (r < 0)
+                return r;
+
+        /* check that the type is correct */
+        switch (rtm_type) {
+                case RTM_NEWADDR:
+                case RTM_GETADDR:
+                case RTM_DELADDR:
+                        switch (type) {
+                                case IFA_ADDRESS:
+                                case IFA_LOCAL:
+                                case IFA_BROADCAST:
+                                case IFA_ANYCAST:
+                                        ifa = NLMSG_DATA(m->hdr);
+
+                                        if (ifa->ifa_family != AF_INET)
+                                                return -EINVAL;
+
+                                        break;
+                                default:
+                                        return -ENOTSUP;
+                        }
+                        break;
+                case RTM_NEWROUTE:
+                case RTM_GETROUTE:
+                case RTM_DELROUTE:
+                        switch (type) {
+                                case RTA_DST:
+                                case RTA_SRC:
+                                case RTA_GATEWAY:
+                                        rtm = NLMSG_DATA(m->hdr);
+
+                                        if (rtm->rtm_family != AF_INET)
+                                                return -EINVAL;
+
+                                        break;
+                                default:
+                                        return -ENOTSUP;
+                        }
+                        break;
+                default:
+                        return -ENOTSUP;
+        }
+
+        r = add_rtattr(m, type, data, sizeof(struct in_addr));
+        if (r < 0)
+                return r;
+
+        return 0;
+}
+
+int sd_rtnl_message_append_in6_addr(sd_rtnl_message *m, unsigned short type, const struct in6_addr *data) {
+        struct ifaddrmsg *ifa;
+        struct rtmsg *rtm;
+        uint16_t rtm_type;
+        int r;
+
+        assert_return(m, -EINVAL);
+        assert_return(data, -EINVAL);
+
+        r = sd_rtnl_message_get_type(m, &rtm_type);
+        if (r < 0)
+                return r;
+
+        /* check that the type is correct */
+        switch (rtm_type) {
+                case RTM_NEWADDR:
+                case RTM_GETADDR:
+                case RTM_DELADDR:
+                        switch (type) {
+                                case IFA_ADDRESS:
+                                case IFA_LOCAL:
+                                case IFA_BROADCAST:
+                                case IFA_ANYCAST:
+                                        ifa = NLMSG_DATA(m->hdr);
+
+                                        if (ifa->ifa_family != AF_INET6)
+                                                return -EINVAL;
+
+                                        break;
+                                default:
+                                        return -ENOTSUP;
+                        }
+                        break;
+                case RTM_NEWROUTE:
+                case RTM_GETROUTE:
+                case RTM_DELROUTE:
+                        switch (type) {
+                                case RTA_DST:
+                                case RTA_SRC:
+                                case RTA_GATEWAY:
+                                        rtm = NLMSG_DATA(m->hdr);
+
+                                        if (rtm->rtm_family != AF_INET6)
+                                                return -EINVAL;
+
+                                        break;
+                                default:
+                                        return -ENOTSUP;
+                        }
+                default:
+                        return -ENOTSUP;
+        }
+
+        r = add_rtattr(m, type, data, sizeof(struct in6_addr));
+        if (r < 0)
+                return r;
+
+        return 0;
+}
+
+int sd_rtnl_message_append_ether_addr(sd_rtnl_message *m, unsigned short type, const struct ether_addr *data) {
+        uint16_t rtm_type;
+        int r;
+
+        assert_return(m, -EINVAL);
+        assert_return(data, -EINVAL);
+
+        sd_rtnl_message_get_type(m, &rtm_type);
+
+        switch (rtm_type) {
+                case RTM_NEWLINK:
+                case RTM_SETLINK:
+                case RTM_DELLINK:
+                case RTM_GETLINK:
+                        switch (type) {
+                                case IFLA_ADDRESS:
+                                case IFLA_BROADCAST:
+                                        break;
+                                default:
+                                        return -ENOTSUP;
+                        }
+                        break;
+                default:
+                        return -ENOTSUP;
+        }
+
+        r = add_rtattr(m, type, data, ETH_ALEN);
+        if (r < 0)
+                return r;
+
+        return 0;
+}
+
+int sd_rtnl_message_open_container(sd_rtnl_message *m, unsigned short type) {
+        uint16_t rtm_type;
+
+        assert_return(m, -EINVAL);
+        assert_return(!CURRENT_CONTAINER(m), -EINVAL);
+
+        sd_rtnl_message_get_type(m, &rtm_type);
+
+        if (message_type_is_link(rtm_type)) {
+                if (type == IFLA_LINKINFO)
+                        return add_rtattr(m, type, NULL, 0);
+                else
+                        return -ENOTSUP;
+        } else
+                return -ENOTSUP;
+
+        return 0;
+}
+
+int sd_rtnl_message_close_container(sd_rtnl_message *m) {
+        assert_return(m, -EINVAL);
+        assert_return(CURRENT_CONTAINER(m), -EINVAL);
+
+        m->container_offset = 0;
+
+        return 0;
+}
+
+int sd_rtnl_message_read(sd_rtnl_message *m, unsigned short *type, void **data) {
+        size_t remaining_size;
+        uint16_t rtm_type;
+        int r;
+
+        assert(m);
+        assert(m->next_rta_offset);
+        assert(type);
+        assert(data);
+
+        remaining_size = m->hdr->nlmsg_len - m->next_rta_offset;
+
+        if (!RTA_OK(NEXT_RTA(m), remaining_size))
+                return 0;
+
+        /* make sure we don't try to read a container
+         * TODO: add support for entering containers for reading */
+        r = sd_rtnl_message_get_type(m, &rtm_type);
+        if (r < 0)
+                return r;
+
+        if (message_type_is_link(rtm_type) &&
+            NEXT_RTA(m)->rta_type == IFLA_LINKINFO)
+               return -EINVAL;
+
+        *data = RTA_DATA(NEXT_RTA(m));
+        *type = NEXT_RTA(m)->rta_type;
+
+        UPDATE_RTA(m, RTA_NEXT(NEXT_RTA(m), remaining_size));
+
+        return 1;
+}
+
+uint32_t message_get_serial(sd_rtnl_message *m) {
+        assert(m);
+        assert(m->hdr);
+
+        return m->hdr->nlmsg_seq;
+}
+
+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)
+                return 0;
+
+        err = NLMSG_DATA(m->hdr);
+
+        return err->error;
+}
+
+int message_seal(sd_rtnl *nl, sd_rtnl_message *m) {
+        assert(nl);
+        assert(m);
+        assert(m->hdr);
+
+        if (m->sealed)
+                return -EPERM;
+
+        m->hdr->nlmsg_seq = nl->serial++;
+        m->sealed = true;
+
+        return 0;
+}
+
+static int message_receive_need(sd_rtnl *rtnl, size_t *need) {
+        assert(rtnl);
+        assert(need);
+
+        /* ioctl(rtnl->fd, FIONREAD, &need)
+           Does not appear to work on netlink sockets. libnl uses
+           MSG_PEEK instead. I don't know if that is worth the
+           extra roundtrip.
+
+           For now we simply use the maximum message size the kernel
+           may use (NLMSG_GOODSIZE), and then realloc to the actual
+           size after reading the message (hence avoiding huge memory
+           usage in case many small messages are kept around) */
+        *need = page_size();
+        if (*need > 8192UL)
+                *need = 8192UL;
+
+        return 0;
+}
+
+/* returns the number of bytes sent, or a negative error code */
+int socket_write_message(sd_rtnl *nl, sd_rtnl_message *m) {
+        union {
+                struct sockaddr sa;
+                struct sockaddr_nl nl;
+        } addr = {
+                .nl.nl_family = AF_NETLINK,
+        };
+        ssize_t k;
+
+        assert(nl);
+        assert(m);
+        assert(m->hdr);
+
+        k = sendto(nl->fd, m->hdr, m->hdr->nlmsg_len,
+                        0, &addr.sa, sizeof(addr));
+        if (k < 0)
+                return (errno == EAGAIN) ? 0 : -errno;
+
+        return k;
+}
+
+/* On success, the number of bytes received is returned and *ret points to the received message
+ * which has a valid header and the correct size.
+ * If nothing useful was received 0 is returned.
+ * On failure, a negative error code is returned.
+ */
+int socket_read_message(sd_rtnl *nl, sd_rtnl_message **ret) {
+        sd_rtnl_message *m;
+        union {
+                struct sockaddr sa;
+                struct sockaddr_nl nl;
+        } addr;
+        socklen_t addr_len;
+        int r;
+        ssize_t k;
+        size_t need;
+
+        assert(nl);
+        assert(ret);
+
+        r = message_receive_need(nl, &need);
+        if (r < 0)
+                return r;
+
+        r = message_new(&m, need);
+        if (r < 0)
+                return r;
+
+        addr_len = sizeof(addr);
+
+        k = recvfrom(nl->fd, m->hdr, need,
+                        0, &addr.sa, &addr_len);
+        if (k < 0)
+                k = (errno == EAGAIN) ? 0 : -errno; /* no data */
+        else if (k == 0)
+                k = -ECONNRESET; /* connection was closed by the kernel */
+        else if (addr_len != sizeof(addr.nl) ||
+                        addr.nl.nl_family != AF_NETLINK)
+                k = -EIO; /* not a netlink message */
+        else if (addr.nl.nl_pid != 0)
+                k = 0; /* not from the kernel */
+        else if ((size_t) k < sizeof(struct nlmsghdr) ||
+                        (size_t) k < m->hdr->nlmsg_len)
+                k = -EIO; /* too small (we do accept too big though) */
+        else if (m->hdr->nlmsg_pid && m->hdr->nlmsg_pid != nl->sockaddr.nl.nl_pid)
+                k = 0; /* not broadcast and not for us */
+
+        if (k > 0)
+                switch (m->hdr->nlmsg_type) {
+                        struct ifinfomsg *ifi;
+                        struct ifaddrmsg *ifa;
+                        struct rtmsg *rtm;
+
+                        /* check that the size matches the message type */
+                        case NLMSG_ERROR:
+                                if (m->hdr->nlmsg_len < NLMSG_LENGTH(sizeof(struct nlmsgerr)))
+                                        k = -EIO;
+                                break;
+                        case RTM_NEWLINK:
+                        case RTM_SETLINK:
+                        case RTM_DELLINK:
+                        case RTM_GETLINK:
+                                if (m->hdr->nlmsg_len < NLMSG_LENGTH(sizeof(struct ifinfomsg)))
+                                        k = -EIO;
+                                else {
+                                        ifi = NLMSG_DATA(m->hdr);
+                                        UPDATE_RTA(m, IFLA_RTA(ifi));
+                                }
+                                break;
+                        case RTM_NEWADDR:
+                        case RTM_DELADDR:
+                        case RTM_GETADDR:
+                                if (m->hdr->nlmsg_len < NLMSG_LENGTH(sizeof(struct ifaddrmsg)))
+                                        k = -EIO;
+                                else {
+                                        ifa = NLMSG_DATA(m->hdr);
+                                        UPDATE_RTA(m, IFA_RTA(ifa));
+                                }
+                                break;
+                        case RTM_NEWROUTE:
+                        case RTM_DELROUTE:
+                        case RTM_GETROUTE:
+                                if (m->hdr->nlmsg_len < NLMSG_LENGTH(sizeof(struct rtmsg)))
+                                        k = -EIO;
+                                else {
+                                        rtm = NLMSG_DATA(m->hdr);
+                                        UPDATE_RTA(m, RTM_RTA(rtm));
+                                }
+                                break;
+                        case NLMSG_NOOP:
+                                k = 0;
+                                break;
+                        default:
+                                k = 0; /* ignoring message of unknown type */
+                }
+
+        if (k <= 0)
+                sd_rtnl_message_unref(m);
+        else {
+                /* we probably allocated way too much memory, give it back */
+                m->hdr = realloc(m->hdr, m->hdr->nlmsg_len);
+                *ret = m;
+        }
+
+        return k;
+}
+
+int sd_rtnl_message_rewind(sd_rtnl_message *m) {
+        struct ifinfomsg *ifi;
+        struct ifaddrmsg *ifa;
+        struct rtmsg *rtm;
+
+        assert_return(m, -EINVAL);
+        assert_return(m->hdr, -EINVAL);
+
+        switch(m->hdr->nlmsg_type) {
+                case RTM_NEWLINK:
+                case RTM_SETLINK:
+                case RTM_GETLINK:
+                case RTM_DELLINK:
+                        ifi = NLMSG_DATA(m->hdr);
+                        UPDATE_RTA(m, IFLA_RTA(ifi));
+
+                        break;
+                case RTM_NEWADDR:
+                case RTM_GETADDR:
+                case RTM_DELADDR:
+                        ifa = NLMSG_DATA(m->hdr);
+                        UPDATE_RTA(m, IFA_RTA(ifa));
+
+                        break;
+                case RTM_NEWROUTE:
+                case RTM_GETROUTE:
+                case RTM_DELROUTE:
+                        rtm = NLMSG_DATA(m->hdr);
+                        UPDATE_RTA(m, RTM_RTA(rtm));
+
+                        break;
+                default:
+                        return -ENOTSUP;
+        }
+
+        return 0;
+}