In message <[email protected]>, "Dun
n, Jeffrey H." writes:
> Mark,
>
> Could you elaborate on what you mean by "DNS servers just tell the kernel t=
> o fragment at network mtu for UDP/IPv6 and ensure that DF is off for UDP/IP=
> v4." What is the "network MTU?" Also, to which implementations of DNS serv=
> er are you referring?
Cut-and-pasted from BIND's bsd socket implementation.
Mark
#ifdef IPV6_USE_MIN_MTU /* RFC 3542, not too common yet*/
/* use minimum MTU */
if (sock->pf == AF_INET6) {
(void)setsockopt(sock->fd, IPPROTO_IPV6,
IPV6_USE_MIN_MTU,
(void *)&on, sizeof(on));
}
#endif
#if defined(IP_MTU_DISCOVER) && defined(IP_PMTUDISC_DONT)
/*
* Turn off Path MTU discovery on IPv4/UDP sockets.
*/
if (sock->pf == AF_INET) {
int action = IP_PMTUDISC_DONT;
(void)setsockopt(sock->fd, IPPROTO_IP, IP_MTU_DISCOVER,
&action, sizeof(action));
}
#endif
#if defined(IP_DONTFRAG)
/*
* Turn off Path MTU discovery on IPv4/UDP sockets.
*/
if (sock->pf == AF_INET) {
int off = 0;
(void)setsockopt(sock->fd, IPPROTO_IP, IP_DONTFRAG,
&off, sizeof(off));
}
#endif
> Best Regards,=20
> =A0=20
> Jeffrey Dunn=20
> Info Systems Eng., Lead=20
> MITRE Corporation.
> (301) 448-6965 (mobile)
--
Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742 INTERNET: [email protected]
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