Power-saving patch to NTP - NTP

This is a discussion on Power-saving patch to NTP - NTP ; Garrett Wollman wrote: > In article , > Martin Burnicki wrote: > >> AFAIK ntpd has to manage the binding to interfaces at least if autokey is >> enabled since the signature hash also includes the IP address of the ...

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Thread: Power-saving patch to NTP

  1. Re: Power-saving patch to NTP

    Garrett Wollman wrote:
    > In article ,
    > Martin Burnicki wrote:
    >
    >> AFAIK ntpd has to manage the binding to interfaces at least if autokey is
    >> enabled since the signature hash also includes the IP address of the
    >> interface via which a packet is sent.

    >
    > At least some operating systems (don't know about Linux) allow this to
    > be controlled using a control message. For example, from the FreeBSD
    > 6.3 ip(4) manual page:
    >
    > The source address to be used for outgoing UDP datagrams on a socket that
    > is not bound to a specific IP address can be specified as ancillary data
    > with a type code of IP_SENDSRCADDR. The msg_control field in the msghdr
    > structure should point to a buffer that contains a cmsghdr structure fol-
    > lowed by the IP address. The cmsghdr fields should have the following
    > values:
    >
    > cmsg_len = sizeof(struct in_addr)
    > cmsg_level = IPPROTO_IP
    > cmsg_type = IP_SENDSRCADDR
    >
    > For convenience, IP_SENDSRCADDR is defined to have the same value as
    > IP_RECVDSTADDR, so the IP_RECVDSTADDR control message from recvmsg(2) can
    > be used directly as a control message for sendmsg(2).
    >
    > The IPV6_PKTINFO message is used for analogous functions in IPv6.
    >
    > -GAWollman


    We are aware of sendmsg(), recvmsg() and friends. The problem, however,
    is that there are many platforms that do not support this yet. It's a
    major effort to deal with this.

    Danny

  2. Re: Power-saving patch to NTP

    Martin Burnicki wrote:
    > Garrett,
    >
    > Garrett Wollman wrote:
    >> In article ,
    >> Martin Burnicki wrote:
    >>
    >>> AFAIK ntpd has to manage the binding to interfaces at least if autokey is
    >>> enabled since the signature hash also includes the IP address of the
    >>> interface via which a packet is sent.

    >> At least some operating systems (don't know about Linux) allow this to
    >> be controlled using a control message. For example, from the FreeBSD
    >> 6.3 ip(4) manual page:
    >>
    >> The source address to be used for outgoing UDP datagrams on a socket
    >> that is not bound to a specific IP address can be specified as
    >> ancillary data
    >> with a type code of IP_SENDSRCADDR. The msg_control field in the
    >> msghdr structure should point to a buffer that contains a cmsghdr
    >> structure fol-
    >> lowed by the IP address. The cmsghdr fields should have the
    >> following values:
    >>
    >> cmsg_len = sizeof(struct in_addr)
    >> cmsg_level = IPPROTO_IP
    >> cmsg_type = IP_SENDSRCADDR
    >>
    >> For convenience, IP_SENDSRCADDR is defined to have the same value as
    >> IP_RECVDSTADDR, so the IP_RECVDSTADDR control message from recvmsg(2)
    >> can be used directly as a control message for sendmsg(2).
    >>
    >> The IPV6_PKTINFO message is used for analogous functions in IPv6.
    >>
    >> -GAWollman

    >
    > That's interesting.
    >
    > However, I'm neither familiar with those techniques, nor do I know whether
    > such an approach would be useful for ntpd, especially since ntpd is
    > targeted for multiple platforms (Frank? Danny?)
    >
    >
    > Martin


    See BIND9 which uses it where possible. The requirements are different
    on NTP but there are different issues that need to be addressed.

    Danny

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