src/nss-myhostname/netlink.c

/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/

/***
  This file is part of systemd.

  Copyright 2008-2011 Lennart Poettering

  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 <sys/socket.h>
#include <sys/un.h>
#include <asm/types.h>
#include <inttypes.h>
#include <linux/netlink.h>
#include <linux/rtnetlink.h>
#include <string.h>
#include <assert.h>
#include <errno.h>
#include <limits.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <stdlib.h>

#include "ifconf.h"

#define SEQ 4711

static int read_reply(int fd, struct address **list, unsigned *n_list) {
        ssize_t bytes;
        struct cmsghdr *cmsg;
        struct ucred *ucred;
        struct nlmsghdr *p;
        uint8_t cred_buffer[CMSG_SPACE(sizeof(struct ucred))];
        struct {
                struct nlmsghdr hdr;
                struct ifaddrmsg ifaddrmsg;
                uint8_t payload[16*1024];
        } resp;
        struct iovec iov = {
                .iov_base = &resp,
                .iov_len = sizeof(resp),
        };
        struct msghdr msg = {
                .msg_name = NULL,
                .msg_namelen = 0,
                .msg_iov = &iov,
                .msg_iovlen = 1,
                .msg_control = cred_buffer,
                .msg_controllen = sizeof(cred_buffer),
                .msg_flags = 0,
        };

        assert(fd >= 0);
        assert(list);

        bytes = recvmsg(fd, &msg, 0);
        if (bytes < 0)
                return -errno;

        cmsg = CMSG_FIRSTHDR(&msg);
        if (!cmsg || cmsg->cmsg_type != SCM_CREDENTIALS)
                return -EIO;

        ucred = (struct ucred*) CMSG_DATA(cmsg);
        if (ucred->uid != 0 || ucred->pid != 0)
                return 0;

        for (p = &resp.hdr; bytes > 0; p = NLMSG_NEXT(p, bytes)) {
                struct ifaddrmsg *ifaddrmsg;
                struct rtattr *a;
                size_t l;
                void *local = NULL, *address = NULL;

                if (!NLMSG_OK(p, (size_t) bytes))
                        return -EIO;

                if (p->nlmsg_seq != SEQ)
                        continue;

                if (p->nlmsg_type == NLMSG_DONE)
                        return 1;

                if (p->nlmsg_type == NLMSG_ERROR) {
                        struct nlmsgerr *nlmsgerr;

                        nlmsgerr = NLMSG_DATA(p);
                        return -nlmsgerr->error;
                }

                if (p->nlmsg_type != RTM_NEWADDR)
                        continue;

                ifaddrmsg = NLMSG_DATA(p);

                if (ifaddrmsg->ifa_family != AF_INET &&
                    ifaddrmsg->ifa_family != AF_INET6)
                        continue;

                if (ifaddrmsg->ifa_scope == RT_SCOPE_HOST ||
                    ifaddrmsg->ifa_scope == RT_SCOPE_NOWHERE)
                        continue;

                if (ifaddrmsg->ifa_flags & IFA_F_DEPRECATED)
                        continue;

                l = NLMSG_PAYLOAD(p, sizeof(struct ifaddrmsg));
                a = IFA_RTA(ifaddrmsg);

                while (RTA_OK(a, l)) {

                        if (a->rta_type == IFA_ADDRESS)
                                address = RTA_DATA(a);
                        else if (a->rta_type == IFA_LOCAL)
                                local = RTA_DATA(a);

                        a = RTA_NEXT(a, l);
                }

                if (local)
                        address = local;

                if (!address)
                        continue;

                *list = realloc(*list, (*n_list+1) * sizeof(struct address));
                if (!*list)
                        return -ENOMEM;

                (*list)[*n_list].family = ifaddrmsg->ifa_family;
                (*list)[*n_list].scope = ifaddrmsg->ifa_scope;
                memcpy((*list)[*n_list].address,
                       address, ifaddrmsg->ifa_family == AF_INET ? 4 : 16);
                (*list)[*n_list].ifindex = ifaddrmsg->ifa_index;

                (*n_list)++;
        }

        return 0;
}


int ifconf_acquire_addresses(struct address **_list, unsigned *_n_list) {

        struct {
                struct nlmsghdr hdr;
                struct rtgenmsg gen;
        } req = { {
                        .nlmsg_len = NLMSG_LENGTH(sizeof(struct rtgenmsg)),
                        .nlmsg_type = RTM_GETADDR,
                        .nlmsg_flags = NLM_F_REQUEST|NLM_F_DUMP|NLM_F_ACK,
                        .nlmsg_seq = SEQ,
                        .nlmsg_pid = 0,
                }, {
                        .rtgen_family = AF_UNSPEC,
                }
        };
        int r, on = 1;
        struct address *list = NULL;
        unsigned n_list = 0;
        int fd;

        fd = socket(PF_NETLINK, SOCK_DGRAM, NETLINK_ROUTE);
        if (fd < 0)
                return -errno;

        if (setsockopt(fd, SOL_SOCKET, SO_PASSCRED, &on, sizeof(on)) < 0) {
                r = -errno;
                goto finish;
        }

        if (send(fd, &req, req.hdr.nlmsg_len, 0) < 0) {
                r = -errno;
                goto finish;
        }

        while((r = read_reply(fd, &list, &n_list)) == 0)
                ;

finish:
        close(fd);

        if (r < 0) {
                free(list);
                return r;
        }

        if (n_list)
                qsort(list, n_list, sizeof(struct address), address_compare);

        *_list = list;
        *_n_list = n_list;

        return 0;
}