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Disable MTU feedback in IPv6 if the sender writes data that must be fragmented.

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Discussed extensively with KAME.  The API author's intent isn't clear at this
point, so rather than remove the code entirely, #if 0 out and put a big
comment in for now. The IPV6_RECVPATHMTU sockopt is available if the
application wants to be notified of the path MTU to optimize packet sizes.

Thanks to JINMEI Tatuya <jinmei@isl.rdc.toshiba.co.jp> for putting up
with my incessant badgering on this issue, and fenner for pointing out
the API issue and suggesting solutions.
This commit is contained in:
Doug White 2004-10-02 23:45:02 +00:00
parent 96ee6195ef
commit 763f534e3c
1 changed files with 14 additions and 0 deletions
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14
sys/netinet6/ip6_output.c
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@ -1035,8 +1035,10 @@ skip_ipsec2:;
struct ip6_frag *ip6f;
u_int32_t id = htonl(ip6_randomid());
u_char nextproto;
#if 0
struct ip6ctlparam ip6cp;
u_int32_t mtu32;
#endif
int qslots = ifp->if_snd.ifq_maxlen - ifp->if_snd.ifq_len;
/*
@ -1048,12 +1050,24 @@ skip_ipsec2:;
if (mtu > IPV6_MAXPACKET)
mtu = IPV6_MAXPACKET;
#if 0
/*
* It is believed this code is a leftover from the
* development of the IPV6_RECVPATHMTU sockopt and
* associated work to implement RFC3542.
* It's not entirely clear what the intent of the API
* is at this point, so disable this code for now.
* The IPV6_RECVPATHMTU sockopt and/or IPV6_DONTFRAG
* will send notifications if the application requests.
*/
/* Notify a proper path MTU to applications. */
mtu32 = (u_int32_t)mtu;
bzero(&ip6cp, sizeof(ip6cp));
ip6cp.ip6c_cmdarg = (void *)&mtu32;
pfctlinput2(PRC_MSGSIZE, (struct sockaddr *)&ro_pmtu->ro_dst,
(void *)&ip6cp);
#endif
len = (mtu - hlen - sizeof(struct ip6_frag)) & ~7;
if (len < 8) {