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nic_router: handle bad DNS in DHCP ACK gracefully

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The DHCP client of the NIC router used to end up in an uncaught exception if
an IP address in the DNS server option of a DHCP ACK was invalid. This commit
makes the 'Dns_server' constructor (where the exception originated from)
private and instead introduces a public lambda method 'construct' that calls
one lambda argument on success and another on failure. This is also in line
with the most recent changes to the 'find_by_*' methods of other classes in
the NIC router and contributes to the goal of reducing expensive exception
handling.

Fixes #4465
This commit is contained in:
Martin Stein 2022-09-07 10:43:53 +02:00 committed by Norman Feske
parent 054990aafa
commit b82d83e271
5 changed files with 61 additions and 25 deletions
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19
repos/os/src/server/nic_router/dhcp_server.cc
View File

@ -34,14 +34,17 @@ Dhcp_server_base::Dhcp_server_base(Xml_node const &node,
{
node.for_each_sub_node("dns-server", [&] (Xml_node const &sub_node) {
try {
_dns_servers.insert_as_tail(*new (alloc)
Dns_server(sub_node.attribute_value("ip", Ipv4_address())));
} catch (Dns_server::Invalid) {
_invalid(domain, "invalid DNS server entry");
}
Dns_server::construct(
alloc, sub_node.attribute_value("ip", Ipv4_address { }),
[&] /* handle_success */ (Dns_server &server)
{
_dns_servers.insert_as_tail(server);
},
[&] /* handle_failure */ ()
{
_invalid(domain, "invalid DNS server entry");
}
);
});
node.with_optional_sub_node("dns-domain", [&] (Xml_node const &sub_node) {
xml_node_with_attribute(sub_node, "name", [&] (Xml_attribute const &attr) {

6
repos/os/src/server/nic_router/dns.cc
View File

@ -30,11 +30,7 @@ using namespace Genode;
Dns_server::Dns_server(Ipv4_address const &ip)
:
_ip { ip }
{
if (!_ip.valid()) {
throw Invalid { };
}
}
{ }
bool Dns_server::equal_to(Dns_server const &server) const

16
repos/os/src/server/nic_router/dns.h
View File

@ -43,11 +43,23 @@ class Net::Dns_server : private Genode::Noncopyable,
Net::Ipv4_address const _ip;
Dns_server(Net::Ipv4_address const &ip);
public:
struct Invalid : Genode::Exception { };
template <typename HANDLE_SUCCESS_FN,
typename HANDLE_FAILURE_FN>
Dns_server(Net::Ipv4_address const &ip);
static void construct(Genode::Allocator &alloc,
Net::Ipv4_address const &ip,
HANDLE_SUCCESS_FN && handle_success,
HANDLE_FAILURE_FN && handle_failure)
{
if (!ip.valid()) {
handle_failure();
}
handle_success(*new (alloc) Dns_server(ip));
}
bool equal_to(Dns_server const &server) const;

19
repos/os/src/server/nic_router/ipv4_config.cc
View File

@ -48,8 +48,14 @@ Ipv4_config::Ipv4_config(Ipv4_config const &ip_config,
_gateway { ip_config._gateway }
{
ip_config.for_each_dns_server([&] (Dns_server const &dns_server) {
_dns_servers.insert_as_tail(
*new (alloc) Dns_server(dns_server.ip()));
Dns_server::construct(
alloc, dns_server.ip(),
[&] /* handle_success */ (Dns_server &server)
{
_dns_servers.insert_as_tail(server);
},
[&] /* handle_failure */ () { }
);
});
_dns_domain_name.set_to(ip_config.dns_domain_name());
}
@ -69,7 +75,14 @@ Ipv4_config::Ipv4_config(Dhcp_packet &dhcp_ack,
dhcp_ack.option<Dhcp_packet::Dns_server>() };
dns_server.for_each_address([&] (Ipv4_address const &addr) {
_dns_servers.insert_as_tail(*new (alloc) Dns_server(addr));
Dns_server::construct(
alloc, addr,
[&] /* handle_success */ (Dns_server &server)
{
_dns_servers.insert_as_tail(server);
},
[&] /* handle_failure */ () { }
);
});
}
catch (Dhcp_packet::Option_not_found) { }

26
repos/os/src/test/nic_router_dhcp/manager/main.cc
View File

@ -107,11 +107,17 @@ void Local::Main::_handle_router_state()
domain_node.for_each_sub_node(
"dns",
[&] (Xml_node const &dns_node)
{
dns_servers.insert_as_tail(
*new (_heap) Dns_server(dns_node.attribute_value("ip", Ipv4_address { })));
});
{
Dns_server::construct(
_heap, dns_node.attribute_value("ip", Ipv4_address { }),
[&] /* handle_success */ (Dns_server &server)
{
dns_servers.insert_as_tail(server);
},
[&] /* handle_failure */ () { }
);
}
);
/*
* If the new list of DNS servers differs from the stored list,
@ -122,8 +128,14 @@ void Local::Main::_handle_router_state()
_dns_servers.destroy_each(_heap);
dns_servers.for_each([&] (Dns_server const &dns_server) {
_dns_servers.insert_as_tail(
*new (_heap) Dns_server(dns_server.ip()));
Dns_server::construct(
_heap, dns_server.ip(),
[&] /* handle_success */ (Dns_server &server)
{
_dns_servers.insert_as_tail(server);
},
[&] /* handle_failure */ () { }
);
});
_router_config_outdated = true;
}