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nic_router: use exact packet sizes in dhcp client

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The DHCP client used to always send packets with a size of 1024 regardless of
the size of the actual content, which was always significantly lower. 1024
bytes was simply a guess to provide enough space for all types of DHCP client
packets. As we know the exact size of each packet the DHCP client sends even
before packet creation, this commit makes use of the knowledge resulting in
much smaller packets sent by the DHCP client.

Fixes #4619
This commit is contained in:
Martin Stein 2022-09-26 16:03:37 +02:00 committed by Christian Helmuth
parent c7c460f6e0
commit f59ee209d2
2 changed files with 15 additions and 10 deletions
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22
repos/os/src/server/nic_router/dhcp_client.cc
View File

@ -17,8 +17,6 @@
#include <domain.h>
#include <configuration.h>
enum { PKT_SIZE = 1024 };
using namespace Genode;
using namespace Net;
using Message_type = Dhcp_packet::Message_type;
@ -64,17 +62,20 @@ Dhcp_client::Dhcp_client(Cached_timer &timer,
void Dhcp_client::discover()
{
enum { DISCOVER_PKT_SIZE = 309 };
_set_state(State::SELECT, _config().dhcp_discover_timeout());
_send(Message_type::DISCOVER, Ipv4_address(), Ipv4_address(),
Ipv4_address());
Ipv4_address(), DISCOVER_PKT_SIZE);
}
void Dhcp_client::_rerequest(State next_state)
{
enum { REREQUEST_PKT_SIZE = 309 };
_set_state(next_state, _rerequest_timeout(2));
Ipv4_address const client_ip = _domain().ip_config().interface().address;
_send(Message_type::REQUEST, client_ip, Ipv4_address(), client_ip);
_send(Message_type::REQUEST, client_ip, Ipv4_address(), client_ip,
REREQUEST_PKT_SIZE);
}
@ -129,10 +130,11 @@ void Dhcp_client::handle_dhcp_reply(Dhcp_packet &dhcp)
if (msg_type != Message_type::OFFER) {
throw Drop_packet("DHCP client expects an offer");
}
enum { REQUEST_PKT_SIZE = 321 };
_set_state(State::REQUEST, _config().dhcp_request_timeout());
_send(Message_type::REQUEST, Ipv4_address(),
dhcp.option<Dhcp_packet::Server_ipv4>().value(),
dhcp.yiaddr());
dhcp.yiaddr(), REQUEST_PKT_SIZE);
break;
case State::REQUEST:
@ -159,10 +161,11 @@ void Dhcp_client::handle_dhcp_reply(Dhcp_packet &dhcp)
void Dhcp_client::_send(Message_type msg_type,
Ipv4_address client_ip,
Ipv4_address server_ip,
Ipv4_address requested_ip)
Ipv4_address requested_ip,
size_t pkt_size)
{
Mac_address client_mac = _interface.router_mac();
_interface.send(PKT_SIZE, [&] (void *pkt_base, Size_guard &size_guard) {
_interface.send(pkt_size, [&] (void *pkt_base, Size_guard &size_guard) {
/* create ETH header of the request */
Ethernet_frame &eth = Ethernet_frame::construct_at(pkt_base, size_guard);
@ -198,19 +201,20 @@ void Dhcp_client::_send(Message_type msg_type,
dhcp.default_magic_cookie();
/* append DHCP option fields to the request */
enum { MAX_PKT_SIZE = 1024 };
Dhcp_options dhcp_opts(dhcp, size_guard);
dhcp_opts.append_option<Dhcp_packet::Message_type_option>(msg_type);
switch (msg_type) {
case Message_type::DISCOVER:
append_param_req_list(dhcp_opts);
dhcp_opts.append_option<Dhcp_packet::Client_id>(client_mac);
dhcp_opts.append_option<Dhcp_packet::Max_msg_size>(PKT_SIZE - dhcp_off);
dhcp_opts.append_option<Dhcp_packet::Max_msg_size>(MAX_PKT_SIZE - dhcp_off);
break;
case Message_type::REQUEST:
append_param_req_list(dhcp_opts);
dhcp_opts.append_option<Dhcp_packet::Client_id>(client_mac);
dhcp_opts.append_option<Dhcp_packet::Max_msg_size>(PKT_SIZE - dhcp_off);
dhcp_opts.append_option<Dhcp_packet::Max_msg_size>(MAX_PKT_SIZE - dhcp_off);
if (_state == State::REQUEST) {
dhcp_opts.append_option<Dhcp_packet::Requested_addr>(requested_ip);
dhcp_opts.append_option<Dhcp_packet::Server_ipv4>(server_ip);

3
repos/os/src/server/nic_router/dhcp_client.h
View File

@ -54,7 +54,8 @@ class Net::Dhcp_client
void _send(Dhcp_packet::Message_type msg_type,
Ipv4_address client_ip,
Ipv4_address server_ip,
Ipv4_address requested_ip);
Ipv4_address requested_ip,
Genode::size_t pkt_size);
Configuration &_config();