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network/ndisc: do nothing for existing routes if on-link flag is zero

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This effectively reverts commit 155d7a2c049cf866a0bfde8de371f09dfb3b6f29.

From RFC 4861 section 6.3.4:
> Note, however, that a Prefix Information option with the on-link flag
> set to zero conveys no information concerning on-link determination and
> MUST NOT be interpreted to mean that addresses covered by the prefix
> are off-link.

So, we should not drop previously configured routes when receieved a RA
with Prefix Information option without on-link flag.

Closes #28435.
This commit is contained in:
Yu Watanabe 2024-04-12 04:24:57 +09:00
parent 3a768db480
commit 9f368d9eb2
1 changed files with 4 additions and 55 deletions
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59
src/network/networkd-ndisc.c
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@ -1231,56 +1231,6 @@ static int ndisc_router_process_onlink_prefix(Link *link, sd_ndisc_router *rt) {
return 0;
}
static int ndisc_router_drop_onlink_prefix(Link *link, sd_ndisc_router *rt) {
_cleanup_(route_unrefp) Route *route = NULL;
uint8_t prefixlen;
struct in6_addr prefix;
usec_t lifetime_usec;
int r;
assert(link);
assert(link->network);
assert(rt);
/* RFC 4861 section 6.3.4.
* Note, however, that a Prefix Information option with the on-link flag set to zero conveys no
* information concerning on-link determination and MUST NOT be interpreted to mean that addresses
* covered by the prefix are off-link. The only way to cancel a previous on-link indication is to
* advertise that prefix with the L-bit set and the Lifetime set to zero. */
if (!link->network->ndisc_use_onlink_prefix)
return 0;
r = sd_ndisc_router_prefix_get_valid_lifetime(rt, &lifetime_usec);
if (r < 0)
return log_link_warning_errno(link, r, "Failed to get prefix lifetime: %m");
if (lifetime_usec != 0)
return 0;
r = sd_ndisc_router_prefix_get_address(rt, &prefix);
if (r < 0)
return log_link_warning_errno(link, r, "Failed to get prefix address: %m");
r = sd_ndisc_router_prefix_get_prefixlen(rt, &prefixlen);
if (r < 0)
return log_link_warning_errno(link, r, "Failed to get prefix length: %m");
r = route_new(&route);
if (r < 0)
return log_oom();
route->family = AF_INET6;
route->dst.in6 = prefix;
route->dst_prefixlen = prefixlen;
r = ndisc_remove_route(route, link);
if (r < 0)
return log_link_warning_errno(link, r, "Could not remove prefix route: %m");
return 0;
}
static int ndisc_router_process_prefix(Link *link, sd_ndisc_router *rt) {
uint8_t flags, prefixlen;
struct in6_addr a;
@ -1319,12 +1269,11 @@ static int ndisc_router_process_prefix(Link *link, sd_ndisc_router *rt) {
if (r < 0)
return log_link_warning_errno(link, r, "Failed to get RA prefix flags: %m");
if (FLAGS_SET(flags, ND_OPT_PI_FLAG_ONLINK))
if (FLAGS_SET(flags, ND_OPT_PI_FLAG_ONLINK)) {
r = ndisc_router_process_onlink_prefix(link, rt);
else
r = ndisc_router_drop_onlink_prefix(link, rt);
if (r < 0)
return r;
if (r < 0)
return r;
}
if (FLAGS_SET(flags, ND_OPT_PI_FLAG_AUTO)) {
r = ndisc_router_process_autonomous_prefix(link, rt);