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Fix infinite-loop router advert problems.

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The previous code here, which started fast-RA whenever that local
address associated with a DHCP context changed, is very vulnerable
to flapping  due to dynamically created addresses in the same net.

Simplify so that if a context which has never found an interface now
finds one, that gets advertised, but not for other changes. That satisfies
the original intention that prefixes not in place when dnsmasq starts
should be recognised.

Also totally ignore all interfaces where we are configured not to do DHCP,
to preclude flapping of they have prefixes in common with interfaces
where we do DHCP.
This commit is contained in:
Simon Kelley
2020-01-27 23:30:10 +00:00
parent cd672933c9
commit 515ba97595
1 changed files with 11 additions and 4 deletions
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15
src/dhcp6.c
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@@ -658,7 +658,8 @@ static int construct_worker(struct in6_addr *local, int prefix,
char ifrn_name[IFNAMSIZ];
struct in6_addr start6, end6;
struct dhcp_context *template, *context;
struct iname *tmp;
(void)scope;
(void)flags;
(void)valid;
@@ -677,9 +678,15 @@ static int construct_worker(struct in6_addr *local, int prefix,
if (flags & IFACE_DEPRECATED)
return 1;
if (!indextoname(daemon->icmp6fd, if_index, ifrn_name))
return 0;
/* Ignore interfaces where we're not doing RA/DHCP6 */
if (!indextoname(daemon->icmp6fd, if_index, ifrn_name) ||
!iface_check(AF_LOCAL, NULL, ifrn_name, NULL))
return 1;
for (tmp = daemon->dhcp_except; tmp; tmp = tmp->next)
if (tmp->name && wildcard_match(tmp->name, ifrn_name))
return 1;
for (template = daemon->dhcp6; template; template = template->next)
if (!(template->flags & (CONTEXT_TEMPLATE | CONTEXT_CONSTRUCTED)))
{
@@ -689,7 +696,7 @@ static int construct_worker(struct in6_addr *local, int prefix,
is_same_net6(local, &template->end6, template->prefix))
{
/* First time found, do fast RA. */
if (template->if_index != if_index || !IN6_ARE_ADDR_EQUAL(&template->local6, local))
if (template->if_index == 0)
{
ra_start_unsolicited(param->now, template);
param->newone = 1;