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Kernel: Fix up the ICMP implementation to generate correct Echo replies.

Browse source 
Serenity now responds to ping. :^)
This commit is contained in:
Andreas Kling 2019-03-12 11:44:38 +01:00
parent 75e0ddd46a
commit 9858be636f
5 changed files with 66 additions and 28 deletions
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2
Kernel/EthernetFrameHeader.h
View file

@ -26,7 +26,5 @@ private:
dword m_payload[0];
};
typedef dword EthernetFrameCheckSequence;
static_assert(sizeof(EthernetFrameHeader) == 14);

4
Kernel/ICMP.h
View file

@ -23,7 +23,7 @@ public:
void set_code(byte b) { m_code = b; }
word checksum() const { return ntohs(m_checksum); }
void set_checksum(word w) { m_checksum = htons(w); }
void set_checksum(word w) { m_checksum = w; }
const void* payload() const { return this + 1; }
void* payload() { return this + 1; }
@ -31,7 +31,7 @@ public:
private:
byte m_type { 0 };
byte m_code { 0 };
word m_checksum { 0 };
NetworkOrdered<word> m_checksum { 0 };
// NOTE: The rest of the header is 4 bytes
};

52
Kernel/IPv4Packet.h
View file

@ -2,6 +2,7 @@
#include <AK/Types.h>
#include <Kernel/IPv4Address.h>
#include <Kernel/NetworkOrdered.h>
struct IPv4Protocol {
enum {
@ -9,6 +10,8 @@ enum {
};
};
NetworkOrdered<word> internet_checksum(const void*, size_t);
class [[gnu::packed]] IPv4Packet {
public:
byte version() const { return (m_version_and_ihl >> 4) & 0xf; }
@ -17,11 +20,11 @@ public:
byte internet_header_length() const { return m_version_and_ihl & 0xf; }
void set_internet_header_length(byte ihl) { m_version_and_ihl = (m_version_and_ihl & 0xf0) | (ihl & 0x0f); }
word length() const { return ntohs(m_length); }
void set_length(word length) { m_length = htons(length); }
word length() const { return m_length; }
void set_length(word length) { m_length = length; }
word ident() const { return ntohs(m_ident); }
void set_ident(word ident) { m_ident = htons(ident); }
word ident() const { return m_ident; }
void set_ident(word ident) { m_ident = ident; }
byte ttl() const { return m_ttl; }
void set_ttl(byte ttl) { m_ttl = ttl; }
@ -29,8 +32,8 @@ public:
byte protocol() const { return m_protocol; }
void set_protocol(byte protocol) { m_protocol = protocol; }
word checksum() const { return ntohs(m_checksum); }
void set_checksum(word checksum) { m_checksum = htons(checksum); }
word checksum() const { return m_checksum; }
void set_checksum(word checksum) { m_checksum = checksum; }
const IPv4Address& source() const { return m_source; }
void set_source(const IPv4Address& address) { m_source = address; }
@ -41,17 +44,38 @@ public:
void* payload() { return this + 1; }
const void* payload() const { return this + 1; }
NetworkOrdered<word> compute_checksum() const
{
ASSERT(!m_checksum);
return internet_checksum(this, sizeof(IPv4Packet));
}
private:
byte m_version_and_ihl;
byte m_dscp_and_ecn;
word m_length;
word m_ident;
word m_flags_and_fragment;
byte m_ttl;
byte m_protocol;
word m_checksum;
byte m_version_and_ihl { 0 };
byte m_dscp_and_ecn { 0 };
NetworkOrdered<word> m_length;
NetworkOrdered<word> m_ident;
NetworkOrdered<word> m_flags_and_fragment;
byte m_ttl { 0 };
NetworkOrdered<byte> m_protocol;
NetworkOrdered<word> m_checksum;
IPv4Address m_source;
IPv4Address m_destination;
};
static_assert(sizeof(IPv4Packet) == 20);
inline NetworkOrdered<word> internet_checksum(const void* ptr, size_t count)
{
dword checksum = 0;
auto* w = (const word*)ptr;
while (count > 1) {
checksum += convert_between_host_and_network(*w++);
if (checksum & 0x80000000)
checksum = (checksum & 0xffff) | (checksum >> 16);
count -= 2;
}
while (checksum >> 16)
checksum = (checksum & 0xffff) + (checksum >> 16);
return ~checksum & 0xffff;
}

4
Kernel/NetworkAdapter.cpp
View file

@ -14,7 +14,7 @@ NetworkAdapter::~NetworkAdapter()
void NetworkAdapter::send(const MACAddress& destination, const ARPPacket& packet)
{
int size_in_bytes = sizeof(EthernetFrameHeader) + sizeof(ARPPacket) + sizeof(EthernetFrameCheckSequence);
int size_in_bytes = sizeof(EthernetFrameHeader) + sizeof(ARPPacket);
auto* eth = (EthernetFrameHeader*)kmalloc(size_in_bytes);
eth->set_source(mac_address());
eth->set_destination(destination);
@ -26,7 +26,7 @@ void NetworkAdapter::send(const MACAddress& destination, const ARPPacket& packet
void NetworkAdapter::send_ipv4(const MACAddress& destination, const void* packet, size_t packet_size)
{
size_t size_in_bytes = sizeof(EthernetFrameHeader) + packet_size + sizeof(EthernetFrameCheckSequence);
size_t size_in_bytes = sizeof(EthernetFrameHeader) + packet_size;
auto* eth = (EthernetFrameHeader*)kmalloc(size_in_bytes);
eth->set_source(mac_address());
eth->set_destination(destination);

32
Kernel/NetworkTask.cpp
View file

@ -36,7 +36,7 @@ void NetworkTask_main()
sleep(100);
continue;
}
if (packet.size() < (int)(sizeof(EthernetFrameHeader) + sizeof(EthernetFrameCheckSequence))) {
if (packet.size() < (int)(sizeof(EthernetFrameHeader))) {
kprintf("NetworkTask: Packet is too small to be an Ethernet packet! (%d)\n", packet.size());
continue;
}
@ -63,7 +63,7 @@ void NetworkTask_main()
void handle_arp(const EthernetFrameHeader& eth, int frame_size)
{
constexpr int minimum_arp_frame_size = sizeof(EthernetFrameHeader) + sizeof(ARPPacket) + sizeof(EthernetFrameCheckSequence);
constexpr int minimum_arp_frame_size = sizeof(EthernetFrameHeader) + sizeof(ARPPacket);
if (frame_size < minimum_arp_frame_size) {
kprintf("handle_arp: Frame too small (%d, need %d)\n", frame_size, minimum_arp_frame_size);
return;
@ -131,7 +131,7 @@ void handle_arp(const EthernetFrameHeader& eth, int frame_size)
void handle_ipv4(const EthernetFrameHeader& eth, int frame_size)
{
constexpr int minimum_ipv4_frame_size = sizeof(EthernetFrameHeader) + sizeof(IPv4Packet) + sizeof(EthernetFrameCheckSequence);
constexpr int minimum_ipv4_frame_size = sizeof(EthernetFrameHeader) + sizeof(IPv4Packet);
if (frame_size < minimum_ipv4_frame_size) {
kprintf("handle_ipv4: Frame too small (%d, need %d)\n", frame_size, minimum_ipv4_frame_size);
return;
@ -159,14 +159,23 @@ void handle_icmp(const EthernetFrameHeader& eth, int frame_size)
(void)frame_size;
auto& ipv4_packet = *static_cast<const IPv4Packet*>(eth.payload());
auto& icmp_header = *static_cast<const ICMPHeader*>(ipv4_packet.payload());
kprintf("handle_icmp: type=%b, code=%b\n", icmp_header.type(), icmp_header.code());
#ifdef ICMP_DEBUG
kprintf("handle_icmp: source=%s, destination=%d type=%b, code=%b\n",
ipv4_packet.source().to_string().characters(),
ipv4_packet.destination().to_string().characters(),
icmp_header.type(),
icmp_header.code()
);
#endif
auto& e1000 = *E1000NetworkAdapter::the();
if (ipv4_packet.destination() == e1000.ipv4_address()) {
// It's for me!
if (icmp_header.type() == ICMPType::EchoRequest) {
auto& request = reinterpret_cast<const ICMPEchoPacket&>(icmp_header);
kprintf("ICMP echo request: id=%u, seq=%u, len=%u\n", (int)request.identifier, (int)request.sequence_number, ipv4_packet.length() - sizeof(ICMPEchoPacket));
kprintf("handle_icmp: EchoRequest from %s: id=%u, seq=%u\n",
ipv4_packet.source().to_string().characters(),
(word)request.identifier,
(word)request.sequence_number
);
byte* response_buffer = (byte*)kmalloc(ipv4_packet.length());
memset(response_buffer, 0, ipv4_packet.length());
struct [[gnu::packed]] EchoResponse {
@ -180,11 +189,18 @@ void handle_icmp(const EthernetFrameHeader& eth, int frame_size)
response.ipv4.set_destination(ipv4_packet.source());
response.ipv4.set_protocol(IPv4Protocol::ICMP);
response.ipv4.set_length(ipv4_packet.length());
response.ipv4.set_ident(1);
response.ipv4.set_ttl(64);
response.ipv4.set_checksum(response.ipv4.compute_checksum());
response.icmp_echo.header.set_type(ICMPType::EchoReply);
response.icmp_echo.header.set_code(0);
response.icmp_echo.identifier = request.identifier;
response.icmp_echo.sequence_number = request.sequence_number;
memcpy(response.icmp_echo.payload(), request.payload(), ipv4_packet.length() - sizeof(EchoResponse));
size_t icmp_packet_length = ipv4_packet.length() - sizeof(IPv4Packet);
size_t icmp_payload_length = ipv4_packet.length() - sizeof(EchoResponse);
memcpy(response.icmp_echo.payload(), request.payload(), icmp_payload_length);
response.icmp_echo.header.set_checksum(internet_checksum(&response.icmp_echo, icmp_packet_length));
e1000.send_ipv4(eth.source(), response_buffer, ipv4_packet.length());
kfree(response_buffer);
}