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network: Document the lack of actual DAD usage in prefixstable algorithm

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The RFC 7217 (prefixstable) algorithm can use Duplicate Address
Detection to produce multiple candidate addresses, but the implementation
here does not currently employ that mechanism.
This commit is contained in:
Kevin P. Fleming 2020-02-08 15:40:40 -05:00 committed by Yu Watanabe
parent 8dcce054e3
commit 0ddad04eda
1 changed files with 5 additions and 0 deletions
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5
src/network/networkd-ndisc.c
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@ -268,6 +268,11 @@ static int ndisc_router_generate_address(Link *link, unsigned prefixlen, uint32_
ORDERED_HASHMAP_FOREACH(j, link->network->ipv6_tokens, i)
if (j->address_generation_type == IPV6_TOKEN_ADDRESS_GENERATION_PREFIXSTABLE
&& memcmp(&j->prefix, &addr, FAMILY_ADDRESS_SIZE(address->family)) == 0) {
/* While this loop uses dad_counter and a retry limit as specified in RFC 7217, the loop
does not actually attempt Duplicate Address Detection; the counter will be incremented
only when the address generation algorithm produces an invalid address, and the loop
may exit with an address which ends up being unusable due to duplication on the link.
*/
for (; j->dad_counter < DAD_CONFLICTS_IDGEN_RETRIES_RFC7217; j->dad_counter++) {
r = make_stableprivate_address(link, &j->prefix, prefixlen, j->dad_counter, &address->in_addr.in6);
if (r < 0)