genl.c

   1 /*
   2  * This ought to be provided by libnl
   3  */
   4
   5 #include <asm/errno.h>
   6 #include <netlink/genl/genl.h>
   7 #include <netlink/genl/family.h>
   8 #include <netlink/genl/ctrl.h>
   9 #include <netlink/msg.h>
  10 #include <netlink/attr.h>
  11
  12 static int error_handler(struct sockaddr_nl *nla, struct nlmsgerr *err,
  13                          void *arg)
  14 {
  15         int *ret = arg;
  16         *ret = err->error;
  17         return NL_STOP;
  18 }
  19
  20 static int ack_handler(struct nl_msg *msg, void *arg)
  21 {
  22         int *ret = arg;
  23         *ret = 0;
  24         return NL_STOP;
  25 }
  26
  27 struct handler_args {
  28         const char *group;
  29         int id;
  30 };
  31
  32 static int family_handler(struct nl_msg *msg, void *arg)
  33 {
  34         struct handler_args *grp = arg;
  35         struct nlattr *tb[CTRL_ATTR_MAX + 1];
  36         struct genlmsghdr *gnlh = nlmsg_data(nlmsg_hdr(msg));
  37         struct nlattr *mcgrp;
  38         int rem_mcgrp;
  39
  40         nla_parse(tb, CTRL_ATTR_MAX, genlmsg_attrdata(gnlh, 0),
  41                   genlmsg_attrlen(gnlh, 0), NULL);
  42
  43         if (!tb[CTRL_ATTR_MCAST_GROUPS])
  44                 return NL_SKIP;
  45
  46         nla_for_each_nested(mcgrp, tb[CTRL_ATTR_MCAST_GROUPS], rem_mcgrp) {
  47                 struct nlattr *tb_mcgrp[CTRL_ATTR_MCAST_GRP_MAX + 1];
  48
  49                 nla_parse(tb_mcgrp, CTRL_ATTR_MCAST_GRP_MAX,
  50                           nla_data(mcgrp), nla_len(mcgrp), NULL);
  51
  52                 if (!tb_mcgrp[CTRL_ATTR_MCAST_GRP_NAME] ||
  53                     !tb_mcgrp[CTRL_ATTR_MCAST_GRP_ID])
  54                         continue;
  55                 if (strncmp(nla_data(tb_mcgrp[CTRL_ATTR_MCAST_GRP_NAME]),
  56                             grp->group, nla_len(tb_mcgrp[CTRL_ATTR_MCAST_GRP_NAME])))
  57                         continue;
  58                 grp->id = nla_get_u32(tb_mcgrp[CTRL_ATTR_MCAST_GRP_ID]);
  59                 break;
  60         }
  61
  62         return NL_SKIP;
  63 }
  64
  65 int nl_get_multicast_id(struct nl_handle *handle, const char *family, const char *group)
  66 {
  67         struct nl_msg *msg;
  68         struct nl_cb *cb;
  69         int ret, ctrlid;
  70         struct handler_args grp = {
  71                 .group = group,
  72                 .id = -ENOENT,
  73         };
  74
  75         msg = nlmsg_alloc();
  76         if (!msg)
  77                 return -ENOMEM;
  78
  79         cb = nl_cb_alloc(NL_CB_DEFAULT);
  80         if (!cb) {
  81                 ret = -ENOMEM;
  82                 goto out_fail_cb;
  83         }
  84
  85         ctrlid = genl_ctrl_resolve(handle, "nlctrl");
  86
  87         genlmsg_put(msg, 0, 0, ctrlid, 0,
  88                     0, CTRL_CMD_GETFAMILY, 0);
  89
  90         ret = -ENOBUFS;
  91         NLA_PUT_STRING(msg, CTRL_ATTR_FAMILY_NAME, family);
  92
  93         ret = nl_send_auto_complete(handle, msg);
  94         if (ret < 0)
  95                 goto out;
  96
  97         ret = 1;
  98
  99         nl_cb_err(cb, NL_CB_CUSTOM, error_handler, &ret);
 100         nl_cb_set(cb, NL_CB_ACK, NL_CB_CUSTOM, ack_handler, &ret);
 101         nl_cb_set(cb, NL_CB_VALID, NL_CB_CUSTOM, family_handler, &grp);
 102
 103         while (ret > 0)
 104                 nl_recvmsgs(handle, cb);
 105
 106         if (ret == 0)
 107                 ret = grp.id;
 108  nla_put_failure:
 109  out:
 110         nl_cb_put(cb);
 111  out_fail_cb:
 112         nlmsg_free(msg);
 113         return ret;
 114 }