driver.net.proto.icmp¶

ICMP (Internet Control Message Protocol) echo request/reply implementation.

Overview¶

This unit implements ICMP over IPv4 (protocol $01). It supports sending echo requests (type 8) and receiving echo replies (type 0). Up to 256 concurrent pending echo requests are tracked by identifier, each with an optional reply callback and error callback. Incoming echo requests are answered automatically.

Dependencies¶

driver.net
driver.net.types
driver.net.util
driver.net.proto.eth2
driver.net.proto.arp
driver.net.proto.ipv4
syslog

Types¶

TICMPHandler¶

Per-request state tracking:

Field	Type	Description
`identifier`	`uint16`	ICMP identifier field for this request
`OnReply`	`procedure(ctx: PPacketContext)`	Called when a matching echo reply arrives
`OnError`	`procedure(code: uint32)`	Called on routing or resolution failure
`active`	`boolean`	Whether this slot is in use

Error Codes¶

aecFailedToResolveHost, aecNoRouteToHost — passed to the OnError callback.

Functions and Procedures¶

register¶

procedure register;

Registers ICMP as the handler for IPv4 protocol $01 via driver.net.proto.ipv4.registerProtocol.

sendICMPRequest¶

procedure sendICMPRequest(dst_ip: TIPv4Address; identifier, sequence: uint16; OnReply: TICMPReplyCallback; OnError: TICMPErrorCallback);

Sends an ICMP echo request to dst_ip: 1. Determines whether the destination is on the local subnet; if so, resolves the destination MAC via ARP; otherwise uses the gateway MAC. 2. Calls OnError(aecFailedToResolveHost) or OnError(aecNoRouteToHost) if resolution fails. 3. Builds the ICMP header with ICMP_DATA_GENERIC payload, computes checksum, and sends via IPv4. 4. Registers the handler slot in Handlers[identifier].

recv¶

procedure recv(ctx: PPacketContext);

Dispatched by IPv4 for all incoming ICMP packets. Handles: - Type 8 (echo request): Swaps source and destination IP/MAC from the context and sends a type-0 echo reply. - Type 0 (echo reply): Looks up Handlers[identifier], calls the registered OnReply callback, and clears the slot.

Notes¶

Each outstanding request occupies one of 256 slots indexed by the ICMP identifier field. Identifiers above 255 are not tracked.
ICMP data uses the ICMP_DATA_GENERIC constant payload defined in driver.net.types.