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libnetlink.c

/*
 * libnetlink.c   RTnetlink service routines.
 *
 *          This program is free software; you can redistribute it and/or
 *          modify it under the terms of the GNU General Public License
 *          as published by the Free Software Foundation; either version
 *          2 of the License, or (at your option) any later version.
 *
 * Authors: Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru>
 *
 * Modified by Ted Felix (www.tedfelix.com) to fix warnings.
 *
 */

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <syslog.h>
#include <fcntl.h>
#include <net/if_arp.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <string.h>
#include <errno.h>
#include <time.h>
#include <sys/uio.h>

#include "libnetlink.h"

void rtnl_close(struct rtnl_handle *rth)
{
      if (rth->fd >= 0) {
            close(rth->fd);
            rth->fd = -1;
      }
}

int rtnl_open_byproto(struct rtnl_handle *rth, unsigned subscriptions,
                  int protocol)
{
      socklen_t addr_len;
      int sndbuf = 32768;
      int rcvbuf = 32768;

      memset(rth, 0, sizeof(rth));

      rth->fd = socket(AF_NETLINK, SOCK_RAW, protocol);
      if (rth->fd < 0) {
            perror("Cannot open netlink socket");
            return -1;
      }

      if (setsockopt(rth->fd,SOL_SOCKET,SO_SNDBUF,&sndbuf,sizeof(sndbuf)) < 0) {
            perror("SO_SNDBUF");
            return -1;
      }

      if (setsockopt(rth->fd,SOL_SOCKET,SO_RCVBUF,&rcvbuf,sizeof(rcvbuf)) < 0) {
            perror("SO_RCVBUF");
            return -1;
      }

      memset(&rth->local, 0, sizeof(rth->local));
      rth->local.nl_family = AF_NETLINK;
      rth->local.nl_groups = subscriptions;

      if (bind(rth->fd, (struct sockaddr*)&rth->local, sizeof(rth->local)) < 0) {
            perror("Cannot bind netlink socket");
            return -1;
      }
      addr_len = sizeof(rth->local);
      if (getsockname(rth->fd, (struct sockaddr*)&rth->local, &addr_len) < 0) {
            perror("Cannot getsockname");
            return -1;
      }
      if (addr_len != sizeof(rth->local)) {
            fprintf(stderr, "Wrong address length %d\n", addr_len);
            return -1;
      }
      if (rth->local.nl_family != AF_NETLINK) {
            fprintf(stderr, "Wrong address family %d\n", rth->local.nl_family);
            return -1;
      }
      rth->seq = time(NULL);
      return 0;
}

int rtnl_open(struct rtnl_handle *rth, unsigned subscriptions)
{
      return rtnl_open_byproto(rth, subscriptions, NETLINK_ROUTE);
}

int rtnl_wilddump_request(struct rtnl_handle *rth, int family, int type)
{
      struct {
            struct nlmsghdr nlh;
            struct rtgenmsg g;
      } req;
      struct sockaddr_nl nladdr;

      memset(&nladdr, 0, sizeof(nladdr));
      nladdr.nl_family = AF_NETLINK;

      memset(&req, 0, sizeof(req));
      req.nlh.nlmsg_len = sizeof(req);
      req.nlh.nlmsg_type = type;
      req.nlh.nlmsg_flags = NLM_F_ROOT|NLM_F_MATCH|NLM_F_REQUEST;
      req.nlh.nlmsg_pid = 0;
      req.nlh.nlmsg_seq = rth->dump = ++rth->seq;
      req.g.rtgen_family = family;

      return sendto(rth->fd, (void*)&req, sizeof(req), 0,
                  (struct sockaddr*)&nladdr, sizeof(nladdr));
}

int rtnl_send(struct rtnl_handle *rth, const char *buf, int len)
{
      struct sockaddr_nl nladdr;

      memset(&nladdr, 0, sizeof(nladdr));
      nladdr.nl_family = AF_NETLINK;

      return sendto(rth->fd, buf, len, 0, (struct sockaddr*)&nladdr, sizeof(nladdr));
}

int rtnl_dump_request(struct rtnl_handle *rth, int type, void *req, int len)
{
      struct nlmsghdr nlh;
      struct sockaddr_nl nladdr;
      struct iovec iov[2] = {
            { .iov_base = &nlh, .iov_len = sizeof(nlh) },
            { .iov_base = req, .iov_len = len }
      };
      struct msghdr msg = {
            .msg_name = &nladdr,
            .msg_namelen =    sizeof(nladdr),
            .msg_iov = iov,
            .msg_iovlen = 2,
      };

      memset(&nladdr, 0, sizeof(nladdr));
      nladdr.nl_family = AF_NETLINK;

      nlh.nlmsg_len = NLMSG_LENGTH(len);
      nlh.nlmsg_type = type;
      nlh.nlmsg_flags = NLM_F_ROOT|NLM_F_MATCH|NLM_F_REQUEST;
      nlh.nlmsg_pid = 0;
      nlh.nlmsg_seq = rth->dump = ++rth->seq;

      return sendmsg(rth->fd, &msg, 0);
}

int rtnl_dump_filter(struct rtnl_handle *rth,
                 rtnl_filter_t filter,
                 void *arg1,
                 rtnl_filter_t junk,
                 void *arg2)
{
      struct sockaddr_nl nladdr;
      struct iovec iov;
      struct msghdr msg = {
            .msg_name = &nladdr,
            .msg_namelen = sizeof(nladdr),
            .msg_iov = &iov,
            .msg_iovlen = 1,
      };
      char buf[16384];

      iov.iov_base = buf;
      while (1) {
            int status;
            struct nlmsghdr *h;

            iov.iov_len = sizeof(buf);
            status = recvmsg(rth->fd, &msg, 0);

            if (status < 0) {
                  if (errno == EINTR)
                        continue;
                  perror("OVERRUN");
                  continue;
            }

            if (status == 0) {
                  fprintf(stderr, "EOF on netlink\n");
                  return -1;
            }

            h = (struct nlmsghdr*)buf;
            while (NLMSG_OK(h, (unsigned)status)) {
                  int err;

                  if (nladdr.nl_pid != 0 ||
                      h->nlmsg_pid != rth->local.nl_pid ||
                      h->nlmsg_seq != rth->dump) {
                        if (junk) {
                              err = junk(&nladdr, h, arg2);
                              if (err < 0)
                                    return err;
                        }
                        goto skip_it;
                  }

                  if (h->nlmsg_type == NLMSG_DONE)
                        return 0;
                  if (h->nlmsg_type == NLMSG_ERROR) {
                        struct nlmsgerr *msgerr = (struct nlmsgerr*)NLMSG_DATA(h);
                        if (h->nlmsg_len < NLMSG_LENGTH(sizeof(struct nlmsgerr))) {
                              fprintf(stderr, "ERROR truncated\n");
                        } else {
                              errno = -msgerr->error;
                              perror("RTNETLINK answers");
                        }
                        return -1;
                  }
                  err = filter(&nladdr, h, arg1);
                  if (err < 0)
                        return err;

skip_it:
                  h = NLMSG_NEXT(h, status);
            }
            if (msg.msg_flags & MSG_TRUNC) {
                  fprintf(stderr, "Message truncated\n");
                  continue;
            }
            if (status) {
                  fprintf(stderr, "!!!Remnant of size %d\n", status);
                  exit(1);
            }
      }
}

int rtnl_talk(struct rtnl_handle *rtnl, struct nlmsghdr *n, pid_t peer,
            unsigned groups, struct nlmsghdr *answer,
            rtnl_filter_t junk,
            void *jarg)
{
      int status;
      unsigned seq;
      struct nlmsghdr *h;
      struct sockaddr_nl nladdr;
      struct iovec iov = {
            .iov_base = (void*) n,
            .iov_len = n->nlmsg_len
      };
      struct msghdr msg = {
            .msg_name = &nladdr,
            .msg_namelen = sizeof(nladdr),
            .msg_iov = &iov,
            .msg_iovlen = 1,
      };
      char   buf[16384];

      memset(&nladdr, 0, sizeof(nladdr));
      nladdr.nl_family = AF_NETLINK;
      nladdr.nl_pid = peer;
      nladdr.nl_groups = groups;

      n->nlmsg_seq = seq = ++rtnl->seq;

      if (answer == NULL)
            n->nlmsg_flags |= NLM_F_ACK;

      status = sendmsg(rtnl->fd, &msg, 0);

      if (status < 0) {
            perror("Cannot talk to rtnetlink");
            return -1;
      }

      memset(buf,0,sizeof(buf));

      iov.iov_base = buf;

      while (1) {
            iov.iov_len = sizeof(buf);
            status = recvmsg(rtnl->fd, &msg, 0);

            if (status < 0) {
                  if (errno == EINTR)
                        continue;
                  perror("OVERRUN");
                  continue;
            }
            if (status == 0) {
                  fprintf(stderr, "EOF on netlink\n");
                  return -1;
            }
            if (msg.msg_namelen != sizeof(nladdr)) {
                  fprintf(stderr, "sender address length == %d\n", msg.msg_namelen);
                  exit(1);
            }
            for (h = (struct nlmsghdr*)buf; (unsigned)status >= sizeof(*h); ) {
                  int err;
                  int len = h->nlmsg_len;
                  int l = len - sizeof(*h);

                  if (l<0 || len>status) {
                        if (msg.msg_flags & MSG_TRUNC) {
                              fprintf(stderr, "Truncated message\n");
                              return -1;
                        }
                        fprintf(stderr, "!!!malformed message: len=%d\n", len);
                        exit(1);
                  }

                  if (nladdr.nl_pid != (unsigned)peer ||
                      h->nlmsg_pid != rtnl->local.nl_pid ||
                      h->nlmsg_seq != seq) {
                        if (junk) {
                              err = junk(&nladdr, h, jarg);
                              if (err < 0)
                                    return err;
                        }
                        /* Don't forget to skip that message. */
                        status -= NLMSG_ALIGN(len);
                        h = (struct nlmsghdr*)((char*)h + NLMSG_ALIGN(len));
                        continue;
                  }

                  if (h->nlmsg_type == NLMSG_ERROR) {
                        struct nlmsgerr *msgerr = (struct nlmsgerr*)NLMSG_DATA(h);
                        if ((unsigned)l < sizeof(struct nlmsgerr)) {
                              fprintf(stderr, "ERROR truncated\n");
                        } else {
                              errno = -msgerr->error;
                              if (errno == 0) {
                                    if (answer)
                                          memcpy(answer, h, h->nlmsg_len);
                                    return 0;
                              }
                              perror("RTNETLINK1 answers");
                        }
                        return -1;
                  }
                  if (answer) {
                        memcpy(answer, h, h->nlmsg_len);
                        return 0;
                  }

                  fprintf(stderr, "Unexpected reply!!!\n");

                  status -= NLMSG_ALIGN(len);
                  h = (struct nlmsghdr*)((char*)h + NLMSG_ALIGN(len));
            }
            if (msg.msg_flags & MSG_TRUNC) {
                  fprintf(stderr, "Message truncated\n");
                  continue;
            }
            if (status) {
                  fprintf(stderr, "!!!Remnant of size %d\n", status);
                  exit(1);
            }
      }
}

int rtnl_listen(struct rtnl_handle *rtnl,
            rtnl_filter_t handler,
            void *jarg)
{
      int status;
      struct nlmsghdr *h;
      struct sockaddr_nl nladdr;
      struct iovec iov;
      struct msghdr msg = {
            .msg_name = &nladdr,
            .msg_namelen = sizeof(nladdr),
            .msg_iov = &iov,
            .msg_iovlen = 1,
      };
      char   buf[8192];

      memset(&nladdr, 0, sizeof(nladdr));
      nladdr.nl_family = AF_NETLINK;
      nladdr.nl_pid = 0;
      nladdr.nl_groups = 0;

      iov.iov_base = buf;
      while (1) {
            iov.iov_len = sizeof(buf);
            status = recvmsg(rtnl->fd, &msg, 0);

            if (status < 0) {
                  if (errno == EINTR)
                        continue;
                  perror("OVERRUN");
                  continue;
            }
            if (status == 0) {
                  fprintf(stderr, "EOF on netlink\n");
                  return -1;
            }
            if (msg.msg_namelen != sizeof(nladdr)) {
                  fprintf(stderr, "Sender address length == %d\n", msg.msg_namelen);
                  exit(1);
            }
            for (h = (struct nlmsghdr*)buf; (unsigned)status >= sizeof(*h); ) {
                  int err;
                  int len = h->nlmsg_len;
                  int l = len - sizeof(*h);

                  if (l<0 || len>status) {
                        if (msg.msg_flags & MSG_TRUNC) {
                              fprintf(stderr, "Truncated message\n");
                              return -1;
                        }
                        fprintf(stderr, "!!!malformed message: len=%d\n", len);
                        exit(1);
                  }

                  err = handler(&nladdr, h, jarg);
                  if (err < 0)
                        return err;

                  status -= NLMSG_ALIGN(len);
                  h = (struct nlmsghdr*)((char*)h + NLMSG_ALIGN(len));
            }
            if (msg.msg_flags & MSG_TRUNC) {
                  fprintf(stderr, "Message truncated\n");
                  continue;
            }
            if (status) {
                  fprintf(stderr, "!!!Remnant of size %d\n", status);
                  exit(1);
            }
      }
}

int rtnl_from_file(FILE *rtnl, rtnl_filter_t handler,
               void *jarg)
{
      int status;
      struct sockaddr_nl nladdr;
      char   buf[8192];
      struct nlmsghdr *h = (void*)buf;

      memset(&nladdr, 0, sizeof(nladdr));
      nladdr.nl_family = AF_NETLINK;
      nladdr.nl_pid = 0;
      nladdr.nl_groups = 0;

      while (1) {
            int err, len, type;
            int l;

            status = fread(&buf, 1, sizeof(*h), rtnl);

            if (status < 0) {
                  if (errno == EINTR)
                        continue;
                  perror("rtnl_from_file: fread");
                  return -1;
            }
            if (status == 0)
                  return 0;

            len = h->nlmsg_len;
            type= h->nlmsg_type;
            l = len - sizeof(*h);

            if (l<0 || (unsigned)len>sizeof(buf)) {
                  fprintf(stderr, "!!!malformed message: len=%d @%lu\n",
                        len, ftell(rtnl));
                  return -1;
            }

            status = fread(NLMSG_DATA(h), 1, NLMSG_ALIGN(l), rtnl);

            if (status < 0) {
                  perror("rtnl_from_file: fread");
                  return -1;
            }
            if (status < l) {
                  fprintf(stderr, "rtnl-from_file: truncated message\n");
                  return -1;
            }

            err = handler(&nladdr, h, jarg);
            if (err < 0)
                  return err;
      }
}

int addattr32(struct nlmsghdr *n, int maxlen, int type, __u32 data)
{
      int len = RTA_LENGTH(4);
      struct rtattr *rta;
      if ((int)NLMSG_ALIGN(n->nlmsg_len) + len > maxlen) {
            fprintf(stderr,"addattr32: Error! max allowed bound %d exceeded\n",maxlen);
            return -1;
      }
      rta = NLMSG_TAIL(n);
      rta->rta_type = type;
      rta->rta_len = len;
      memcpy(RTA_DATA(rta), &data, 4);
      n->nlmsg_len = NLMSG_ALIGN(n->nlmsg_len) + len;
      return 0;
}

int addattr_l(struct nlmsghdr *n, int maxlen, int type, const void *data,
            int alen)
{
      int len = RTA_LENGTH(alen);
      struct rtattr *rta;

      if ((int)NLMSG_ALIGN(n->nlmsg_len) + RTA_ALIGN(len) > maxlen) {
            fprintf(stderr, "addattr_l ERROR: message exceeded bound of %d\n",maxlen);
            return -1;
      }
      rta = NLMSG_TAIL(n);
      rta->rta_type = type;
      rta->rta_len = len;
      memcpy(RTA_DATA(rta), data, alen);
      n->nlmsg_len = NLMSG_ALIGN(n->nlmsg_len) + RTA_ALIGN(len);
      return 0;
}

int addraw_l(struct nlmsghdr *n, int maxlen, const void *data, int len)
{
      if ((int)NLMSG_ALIGN(n->nlmsg_len) + NLMSG_ALIGN(len) > maxlen) {
            fprintf(stderr, "addraw_l ERROR: message exceeded bound of %d\n",maxlen);
            return -1;
      }

      memcpy(NLMSG_TAIL(n), data, len);
      memset((void *) NLMSG_TAIL(n) + len, 0, NLMSG_ALIGN(len) - len);
      n->nlmsg_len = NLMSG_ALIGN(n->nlmsg_len) + NLMSG_ALIGN(len);
      return 0;
}

int rta_addattr32(struct rtattr *rta, int maxlen, int type, __u32 data)
{
      int len = RTA_LENGTH(4);
      struct rtattr *subrta;

      if (RTA_ALIGN(rta->rta_len) + len > maxlen) {
            fprintf(stderr,"rta_addattr32: Error! max allowed bound %d exceeded\n",maxlen);
            return -1;
      }
      subrta = (struct rtattr*)(((char*)rta) + RTA_ALIGN(rta->rta_len));
      subrta->rta_type = type;
      subrta->rta_len = len;
      memcpy(RTA_DATA(subrta), &data, 4);
      rta->rta_len = NLMSG_ALIGN(rta->rta_len) + len;
      return 0;
}

int rta_addattr_l(struct rtattr *rta, int maxlen, int type,
              const void *data, int alen)
{
      struct rtattr *subrta;
      int len = RTA_LENGTH(alen);

      if (RTA_ALIGN(rta->rta_len) + RTA_ALIGN(len) > maxlen) {
            fprintf(stderr,"rta_addattr_l: Error! max allowed bound %d exceeded\n",maxlen);
            return -1;
      }
      subrta = (struct rtattr*)(((char*)rta) + RTA_ALIGN(rta->rta_len));
      subrta->rta_type = type;
      subrta->rta_len = len;
      memcpy(RTA_DATA(subrta), data, alen);
      rta->rta_len = NLMSG_ALIGN(rta->rta_len) + RTA_ALIGN(len);
      return 0;
}

int parse_rtattr(struct rtattr *tb[], int max, struct rtattr *rta, int len)
{
      memset(tb, 0, sizeof(struct rtattr *) * (max + 1));
      while (RTA_OK(rta, len)) {
            if (rta->rta_type <= max)
                  tb[rta->rta_type] = rta;
            rta = RTA_NEXT(rta,len);
      }
      if (len)
            fprintf(stderr, "!!!Deficit %d, rta_len=%d\n", len, rta->rta_len);
      return 0;
}

int parse_rtattr_byindex(struct rtattr *tb[], int max, struct rtattr *rta, int len)
{
      int i = 0;

      memset(tb, 0, sizeof(struct rtattr *) * max);
      while (RTA_OK(rta, len)) {
            if (rta->rta_type <= max && i < max)
                  tb[i++] = rta;
            rta = RTA_NEXT(rta,len);
      }
      if (len)
            fprintf(stderr, "!!!Deficit %d, rta_len=%d\n", len, rta->rta_len);
      return i;
}

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