iothradvd

A Router Advertisement Daemon for the Internet of Threads

iothradvd is a router advertisement daemon for IPv6. It listens for router solicitation messages and sends router advertisements as described in "Neighbor Discovery for IP Version 6 (IPv6)" (RFC 4861). Hosts can automatically configure their addresses, prefixes and other parameters using the values acquired by RA messages.

iothradvd is a daemon in the Internet of Threads definition: given that the process is a network node by its own, iothradvd runs as a thread.

libiothradvd: the IoTh router advertisement daemon library.

The daemon is started using one of the following functions:

struct iothradvd *iothradvd_start(
     struct ioth *stack, unsigned int ifindex, int period,
     struct iothradata *data,
     struct iothraprefix *pdata, int npdata);

struct iothradvd *iothradvd_vdestart(
     char *vnl, void *macaddr, int period,
     struct iothradata *data,
     struct iothraprefix *pdata, int npdata);

The former function, iothradvd_start uses libioth, while the latter, iothradvd_vdestart is implemented using VDE and an emulation of IPv6.

iothradvd_start needs two specific arguments:

• stack: the ioth stack (see libioth), the kernel stack is used if this argument is NULL.

• ifindex: the interface index (see if_nametoindex(3) or ioth_if_nametoindex).

iothradvd_vdestart has two specific arguments:

• vnl: the virtual network locator.

• macaddr: the MAC address (six bytes).

The remaining arguments are common among the two implementations:

• period: iothradvd generates non solicited advertisement packets if not 0. The value is the period in seconds between two consecutive unsolicited packets. If the value is 0 the daemon only replies to router solicitation packets.

• data: data about the netowrk, a pointer to a struct iothradata

• pdata: data of prefixes, it is an array of struct iothraprefix

• npdata: is the number of elements in pdata

struct iothradata:

    struct iothradata {
      uint8_t curhoplimit;
      uint8_t flags;
      uint16_t router_lifetime;
      uint32_t reachable;
      uint32_t retransmit;
      uint32_t mtu;
   };

• curhoplimit: hoplimit for router advertisement packets.

• flags: it is a bit field. The value can be a bitwise-or combination of ND_RA_FLAG_MANAGED, ND_RA_FLAG_OTHER,ND_RA_FLAG_HOME_AGENT and other values defined in RFC 4861 section 4.2 and further modifications.

• router_lifetime: It is the lifetime associated with the default router in units of seconds (RFC 4861)

• reachable: it is the time, in milliseconds, that a node assumes a neighbor is reachable after having received a reachability confirmation (RFC 4861).

• retransmit: it is the time, in milliseconds, between retransmitted Neighbor Solicitation messages. (RFC 4861).

• mtu: it is the MTU advertised for the network.

struct iothraprefix

    struct iothraprefix {
      struct in6_addr prefix;
      uint8_t prefixlen;
      uint8_t flags;
      uint32_t valid_time;
      uint32_t preferred_time;
    };

• prefix: the IPv6 prefix to be advertised.

• prefixlen: the number of leading bits in the Prefix that are valid. The value ranges from 0 to 128.

• flags: it is a bit field. The value can be a bitwise-or combination of ND_OPT_PI_FLAG_ONLINK, ND_OPT_PI_FLAG_AUTO and ND_OPT_PI_FLAG_RADDR (RFC 4861 section 4,6,2 and further modification)

• valid_time: it is length of time in seconds (relative to the time the packet is sent) that the prefix is valid for the purpose of on-link determination. A value of all one bits (0xffffffff) represents infinity. (RFC 4861)

• preferred_time: it is the length of time in seconds (relative to the time the packet is sent) that addresses generated from the prefix via stateless address autoconfiguration remain preferred. A value of all one bits (0xffffffff) represents infinity. (RFC 4861)

iothradvd command

The program named iothradvd is router advertisement daemon implementation for IPv6 based on libiothradvd. It listens to router solicitations and sends router advertisements as described in "Neighbor Discovery for IP Version 6 (IPv6)" (RFC 4861)

• iothradvd can be used to test the library features (libiothradvd)
• its source code is a tutorial on how to use libiothradvd
• if can be used instead of radvd(8)

Command line syntax:

   iothradvd OPTIONS prefix <prefix> ....

Each prefix is defined as addr/len/flags/valid/preferred:

• addr: IPv6 addr
• len : prefix length
• flags <flag codes>: L=on link, A=autoconf, R=addr is router
• valid: valid lifetime (secs)
• preferred: preferred lifetime (secs)

Example: fc01::/64/LA/86400/14400

Options

• --stack|-s <ioth_stack_conf> or VNL. it uses an ipv6 emulation if this is a VDE VNL.
• --rcfile|-f <conffile>
• --daemon|-d
• --pidfile|-p <pidfile>
• --verbose|-v
• --period|-P <period in seconds>
• --iface|-i <interface> only for ioth stack, default value vde0
• --macaddr|-m <mac_address> only for vde emulation set the radvd MAC addr
• --hoplimit|-H <current hop limit>
• --flags|-F <flag codes> M=managed, O=other H=home h=hiprio l=loprio P=proxy
• --lifetime|-L <router lifetime> secs
• --reachable|-r <reachable time> msecs
• --retransmit|-R <retransmit time> msecs
• `--mtu|-M

configuration file syntax

The configuration file loaded using the option -f or --rcfile has the following syntax:

• lines beginning by '#' are comments.
• the other lines have a tag and may have an argument if required by the tag. The tags have the same name of the long options (--something) of the command line, their arguments have the same syntax and meaning of each equivalent command line option. Command line arguments have priority on the configuration file specifications: if the same tag is specified as a command line option and in the configuration file, the value in the command line is taken and the other ignored. prefix is the only tag that can appear several times in the configuration file.

      stack      <ioth_stack_conf>
      prefix     <prefix specification: addr/len/flags/valid/preferred>
      daemon
      pidfile    <pidfile>
      verbose
      period     <period in seconds>
      iface      <interface>
      macaddr    <mac address
      hoplimit   <value of hop limit>
      flags      <flag codes>
      lifetime   <router lifetime in secs>
      reachable  <reachable time in msecs>
      retransmit <retransmit time in msec>
      mtu        <mtu>

How to install

iothradvd depends on the following libraries, that must be installed in advance:

• libioth
• vdeplug4
• iothconf

iothradvd uses the cmake building system.

$ mkdir build
$ cd build
$ cmake ..
$ make
$ sudo make install