Pascal.Andre at hp
Jun 5, 2009, 5:29 AM
Post #2 of 6
(1176 views)
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Re: Checksum not computed in ICMPv6 neighbor advertisement
[In reply to]
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Hi Dejan,
Thanks for your quick reply.
Sorry, I never tried with a mask of 128.
Regards,
Pascal
> -----Original Message-----
> From: linux-ha-dev-bounces [at] lists
> [mailto:linux-ha-dev-bounces [at] lists] On Behalf Of
> Dejan Muhamedagic
> Sent: Friday, June 05, 2009 1:09 PM
> To: High-Availability Linux Development List
> Subject: Re: [Linux-ha-dev] Checksum not computed in ICMPv6
> neighbor advertisement
>
> Hi Andre,
>
> On Fri, Jun 05, 2009 at 09:34:37AM +0000, Andre, Pascal wrote:
> > Hi,
> >
> > On an Active/Standby platform (using Linux-HA 2.1.4 RHEL5, in my
> > case), when a fail-over/switch-over is initiated and
> standby machine
> > takes over the virtual IP (IPv6), IPv6addr broadcasts an ICMPv6
> > neighbor advertisement message.
> >
> > Unfortunately, this ICMPv6 message has its checksum field set to 0
> > (i.e. not computed). The message is thus discarded by recipients.
> >
> > Maybe this computation should be done by libnet itself.
> > Unfortunately, without much time to investigate libnet, I've added
> > code in resources/OCF/IPv6addr.c in order to compute the
> checksum and
> > provide the result to libnet (as a parameter).
>
> Applied. Many thanks for the patch.
>
> BTW, a user recently complained on the user mailing list
> about not being able to run IPv6addr with mask 128. Did you
> ever experience that? I looked at the code a bit, couldn't
> find a problem. Oh, and it only prints the Generic error
> (exit code 1) and one couldn't figure out anything from the strace.
>
> Cheers,
>
> Dejan
>
> > Regards,
> > Pascal ANDRE
> >
> >
> > --- IPv6addr.c.old 2009-04-30 10:15:16.000000000 +0200
> > +++ IPv6addr.c 2009-04-30 11:45:43.000000000 +0200
> > @@ -381,6 +381,58 @@
> > return OCF_NOT_RUNNING;
> > }
> >
> > +/* compute ICMPv6 checksum */
> > +static uint32_t
> > +cksum_sum(uint16_t *addr, int len, int ntoh) {
> > + uint16_t * w = addr;
> > + uint16_t ret = 0;
> > + uint32_t sum = 0;
> > +
> > + while (len > 1) {
> > + ret = *w++;
> > + if (ntoh) ret = ntohs(ret);
> > + sum += ret;
> > + len -= 2;
> > + }
> > +
> > + if (len == 1) {
> > + *(unsigned char *) (&ret) = *(unsigned char *) w; sum += ret; }
> > +
> > + return sum;
> > +}
> > +
> > +static uint16_t
> > +icmpv6_cksum(struct in6_addr* src_ip, struct
> libnet_in6_addr* dst_ip,
> > +char* payload, int payload_len) { uint32_t sum = 0;
> uint16_t val =
> > +0;
> > +
> > + /* IPv6 pseudo header */
> > + sum += cksum_sum( src_ip->s6_addr16, 16, 1 ); sum += cksum_sum(
> > + (uint16_t *)dst_ip, 16, 1 ); val = payload_len + (2 *
> > + sizeof(uint32_t)); sum += cksum_sum( &val, 2, 0 ); val =
> 58; sum +=
> > + cksum_sum( &val, 2, 0 );
> > +
> > + /* ICMPv6 packet */
> > + val = 0x8800;
> > + sum += cksum_sum( &val, 2, 0 );
> > + val = 0x2000;
> > + sum += cksum_sum( &val, 2, 0 );
> > + sum += cksum_sum( (uint16_t *)payload, payload_len, 1 );
> > +
> > + /* perform 16-bit one's complement of sum */ sum = (sum >> 16) +
> > + (sum & 0xffff); sum += (sum >> 16); val = ~sum;
> > +
> > + return val;
> > +}
> > +
> > /* Send an unsolicited advertisement packet
> > * Please refer to rfc2461
> > */
> > @@ -416,7 +468,7 @@
> >
> > libnet_seed_prand(l);
> > /* 0x2000: RSO */
> > - libnet_build_icmpv4_echo(136,0,0,0x2000,0,(u_int8_t *)payload
> > +
> libnet_build_icmpv4_echo(136,0,icmpv6_cksum(src_ip,&dst_ip,payload,s
> > + izeof(payload)),0x2000,0,(u_int8_t *)payload
> > ,sizeof(payload), l, LIBNET_PTAG_INITIALIZER);
> > libnet_build_ipv6(0,0,LIBNET_ICMPV6_H +
> sizeof(payload),IPPROTO_ICMP6,
> > 255,*(struct libnet_in6_addr*)src_ip,
>
> > _______________________________________________________
> > Linux-HA-Dev: Linux-HA-Dev [at] lists
> > http://lists.linux-ha.org/mailman/listinfo/linux-ha-dev
> > Home Page: http://linux-ha.org/
>
> _______________________________________________________
> Linux-HA-Dev: Linux-HA-Dev [at] lists
> http://lists.linux-ha.org/mailman/listinfo/linux-ha-dev
> Home Page: http://linux-ha.org/
>
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