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[ipv6] Ignore SLAAC on prefixes with an incompatible prefix length

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Experience suggests that routers are often misconfigured to advertise
SLAAC even on prefixes that do not have a SLAAC-compatible prefix
length.  iPXE will currently treat this as an error, resulting in the
prefix being ignored completely.

Handle this misconfiguration by ignoring the autonomous address flag
when the prefix length is unsuitable for SLAAC.

Reported-by: Malte Janduda <mail@janduda.net>
Signed-off-by: Michael Brown <mcb30@ipxe.org>
This commit is contained in:
Michael Brown
2022-09-13 13:25:19 +01:00
parent bc19aeca5f
commit 8f5fc16143
1 changed files with 25 additions and 11 deletions
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36
src/net/ndp.c
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@@ -789,29 +789,43 @@ static int ndp_prefix_fetch_ip6 ( struct settings *settings, void *data,
container_of ( ndpset->settings.parent, struct net_device,
settings.settings );
struct ndp_prefix_information_option *prefix = prefset->prefix;
struct in6_addr ip6;
struct in6_addr *ip6 = &prefix->prefix;
struct in6_addr slaac;
int prefix_len;
int rc;
/* Skip dead prefixes */
if ( ! prefix->valid )
return -ENOENT;
/* Construct IPv6 address via SLAAC, if applicable */
memcpy ( &ip6, &prefix->prefix, sizeof ( ip6 ) );
if ( prefix->flags & NDP_PREFIX_AUTONOMOUS ) {
prefix_len = ipv6_eui64 ( &ip6, netdev );
if ( prefix_len < 0 )
return prefix_len;
if ( prefix_len != prefix->prefix_len )
return -EINVAL;
memcpy ( &slaac, ip6, sizeof ( slaac ) );
prefix_len = ipv6_eui64 ( &slaac, netdev );
if ( prefix_len == prefix->prefix_len ) {
/* Correctly configured prefix: use SLAAC address */
ip6 = &slaac;
} else if ( prefix_len < 0 ) {
/* Link layer does not support SLAAC */
rc = prefix_len;
DBGC ( netdev, "NDP %s does not support SLAAC: %s\n",
netdev->name, strerror ( rc ) );
} else {
/* Prefix length incorrect: assume a badly
* configured router and ignore SLAAC address.
*/
DBGC ( netdev, "NDP %s ignoring misconfigured SLAAC "
"on prefix %s/%d\n", netdev->name,
inet6_ntoa ( ip6 ), prefix->prefix_len );
}
}
/* Fill in IPv6 address */
if ( len > sizeof ( ip6 ) )
len = sizeof ( ip6 );
memcpy ( data, &ip6, len );
if ( len > sizeof ( *ip6 ) )
len = sizeof ( *ip6 );
memcpy ( data, ip6, len );
return sizeof ( ip6 );
return sizeof ( *ip6 );
}
/**