genl.c

/*
 * This ought to be provided by libnl
 */

#include <asm/errno.h>
#include <netlink/genl/genl.h>
#include <netlink/genl/family.h>
#include <netlink/genl/ctrl.h>  
#include <netlink/msg.h>
#include <netlink/attr.h>
#include <linux/genetlink.h>

#include "iw.h"

static int error_handler(struct sockaddr_nl *nla, struct nlmsgerr *err,
			 void *arg)
{
	int *ret = arg;
	*ret = err->error;
	return NL_STOP;
}

static int ack_handler(struct nl_msg *msg, void *arg)
{
	int *ret = arg;
	*ret = 0;
	return NL_STOP;
}

struct handler_args {
	const char *group;
	int id;
};

static int family_handler(struct nl_msg *msg, void *arg)
{
	struct handler_args *grp = arg;
	struct nlattr *tb[CTRL_ATTR_MAX + 1];
	struct genlmsghdr *gnlh = nlmsg_data(nlmsg_hdr(msg));
	struct nlattr *mcgrp;
	int rem_mcgrp;

	nla_parse(tb, CTRL_ATTR_MAX, genlmsg_attrdata(gnlh, 0),
		  genlmsg_attrlen(gnlh, 0), NULL);

        if (!tb[CTRL_ATTR_MCAST_GROUPS])
		return NL_SKIP;

	nla_for_each_nested(mcgrp, tb[CTRL_ATTR_MCAST_GROUPS], rem_mcgrp) {
		struct nlattr *tb_mcgrp[CTRL_ATTR_MCAST_GRP_MAX + 1];

		nla_parse(tb_mcgrp, CTRL_ATTR_MCAST_GRP_MAX,
			  nla_data(mcgrp), nla_len(mcgrp), NULL);

		if (!tb_mcgrp[CTRL_ATTR_MCAST_GRP_NAME] ||
		    !tb_mcgrp[CTRL_ATTR_MCAST_GRP_ID])
			continue;
		if (strncmp(nla_data(tb_mcgrp[CTRL_ATTR_MCAST_GRP_NAME]),
			    grp->group, nla_len(tb_mcgrp[CTRL_ATTR_MCAST_GRP_NAME])))
			continue;
		grp->id = nla_get_u32(tb_mcgrp[CTRL_ATTR_MCAST_GRP_ID]);
		break;
	}
	
	return NL_SKIP;
}

int nl_get_multicast_id(struct nl_sock *sock, const char *family, const char *group)
{
	struct nl_msg *msg;
	struct nl_cb *cb;
	int ret, ctrlid;
	struct handler_args grp = {
		.group = group,
		.id = -ENOENT,
	};

	msg = nlmsg_alloc();
	if (!msg)
		return -ENOMEM;

	cb = nl_cb_alloc(NL_CB_DEFAULT);
	if (!cb) {
		ret = -ENOMEM;
		goto out_fail_cb;
	}

	ctrlid = genl_ctrl_resolve(sock, "nlctrl");

        genlmsg_put(msg, 0, 0, ctrlid, 0,
		    0, CTRL_CMD_GETFAMILY, 0);

	ret = -ENOBUFS;
	NLA_PUT_STRING(msg, CTRL_ATTR_FAMILY_NAME, family);

	ret = nl_send_auto_complete(sock, msg);
	if (ret < 0)
		goto out;

	ret = 1;

	nl_cb_err(cb, NL_CB_CUSTOM, error_handler, &ret);
	nl_cb_set(cb, NL_CB_ACK, NL_CB_CUSTOM, ack_handler, &ret);
	nl_cb_set(cb, NL_CB_VALID, NL_CB_CUSTOM, family_handler, &grp);

	while (ret > 0)
		nl_recvmsgs(sock, cb);

	if (ret == 0)
		ret = grp.id;
 nla_put_failure:
 out:
	nl_cb_put(cb);
 out_fail_cb:
	nlmsg_free(msg);
	return ret;
}