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DHCPClient: Don't reject packets smaller than the max size

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It's acceptable to have less padding in a packet, the only requirement
is to have a single byte of 'END' in the DHCP fields.
This commit is contained in:
AnotherTest 2021-02-15 21:36:57 +03:30 • committed by Andreas Kling
parent c0703f48fe
commit 3440dbb1fc
2 changed files with 8 additions and 4 deletions
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6
Userland/Services/DHCPClient/DHCPv4Client.cpp
View file

@ -53,7 +53,9 @@ static void send(const InterfaceDescriptor& iface, const DHCPv4Packet& packet, C
dst.sin_addr.s_addr = IPv4Address { 255, 255, 255, 255 }.to_u32(); dst.sin_addr.s_addr = IPv4Address { 255, 255, 255, 255 }.to_u32();
memset(&dst.sin_zero, 0, sizeof(dst.sin_zero)); memset(&dst.sin_zero, 0, sizeof(dst.sin_zero));
dbgln_if(DHCPV4CLIENT_DEBUG, "sendto({} bound to {}, ..., {} at {}) = ...?", fd, iface.m_ifname, dst.sin_addr.s_addr, dst.sin_port);
auto rc = sendto(fd, &packet, sizeof(packet), 0, (sockaddr*)&dst, sizeof(dst)); auto rc = sendto(fd, &packet, sizeof(packet), 0, (sockaddr*)&dst, sizeof(dst));
dbgln_if(DHCPV4CLIENT_DEBUG, "sendto({}) = {}", fd, rc);
if (rc < 0) { if (rc < 0) {
dbgln("sendto failed with {}", strerror(errno)); dbgln("sendto failed with {}", strerror(errno));
// FIXME: what do we do here? // FIXME: what do we do here?
@ -113,8 +115,8 @@ DHCPv4Client::DHCPv4Client(Vector<InterfaceDescriptor> ifnames)
m_server->on_ready_to_receive = [this] { m_server->on_ready_to_receive = [this] {
auto buffer = m_server->receive(sizeof(DHCPv4Packet)); auto buffer = m_server->receive(sizeof(DHCPv4Packet));
dbgln("Received {} bytes", buffer.size()); dbgln("Received {} bytes", buffer.size());
if (buffer.size() != sizeof(DHCPv4Packet)) { if (buffer.size() < sizeof(DHCPv4Packet) - DHCPV4_OPTION_FIELD_MAX_LENGTH + 1 || buffer.size() > sizeof(DHCPv4Packet)) {
dbgln("we expected {} bytes, this is a bad packet", sizeof(DHCPv4Packet)); dbgln("we expected {}-{} bytes, this is a bad packet", sizeof(DHCPv4Packet) - DHCPV4_OPTION_FIELD_MAX_LENGTH + 1, sizeof(DHCPv4Packet));
return; return;
} }
auto& packet = *(DHCPv4Packet*)buffer.data(); auto& packet = *(DHCPv4Packet*)buffer.data();

6
Userland/Services/DHCPClient/main.cpp
View file

@ -25,6 +25,7 @@
*/ */
#include "DHCPv4Client.h" #include "DHCPv4Client.h"
#include <AK/Debug.h>
#include <AK/JsonArray.h> #include <AK/JsonArray.h>
#include <AK/JsonObject.h> #include <AK/JsonObject.h>
#include <AK/String.h> #include <AK/String.h>
@ -69,7 +70,7 @@ int main([[maybe_unused]] int argc, [[maybe_unused]] char** argv)
auto file = Core::File::construct("/proc/net/adapters"); auto file = Core::File::construct("/proc/net/adapters");
if (!file->open(Core::IODevice::ReadOnly)) { if (!file->open(Core::IODevice::ReadOnly)) {
warnln("Error: {}", file->error_string()); dbgln("Error: {}", file->error_string());
return 1; return 1;
} }
@ -77,7 +78,7 @@ int main([[maybe_unused]] int argc, [[maybe_unused]] char** argv)
auto json = JsonValue::from_string(file_contents); auto json = JsonValue::from_string(file_contents);
if (!json.has_value() || !json.value().is_array()) { if (!json.has_value() || !json.value().is_array()) {
warnln("Error: No network adapters available"); dbgln("Error: No network adapters available");
return 1; return 1;
} }
@ -90,6 +91,7 @@ int main([[maybe_unused]] int argc, [[maybe_unused]] char** argv)
auto name = if_object.get("name").to_string(); auto name = if_object.get("name").to_string();
auto mac = if_object.get("mac_address").to_string(); auto mac = if_object.get("mac_address").to_string();
dbgln_if(DHCPV4_DEBUG, "Found adapter '{}' with mac {}", name, mac);
ifnames.append({ name, mac_from_string(mac) }); ifnames.append({ name, mac_from_string(mac) });
}); });