bool probe_update_fields(probe_t * probe)
{
return probe_finalize(probe)
&& probe_update_protocol(probe)
&& probe_update_length(probe)
&& probe_update_checksum(probe);
}
bool network_tag_probe(network_t * network, probe_t * probe)
{
uint16_t tag, // Network-side endianness
checksum; // Host-side endianness
size_t payload_size = probe_get_payload_size(probe);
size_t tag_size = sizeof(uint16_t);
size_t num_layers = probe_get_num_layers(probe);
// For probes having a payload of size 0 and a "body" field (like icmp)
layer_t * last_layer;
bool tag_in_body = false;
/* The probe gets assigned a unique tag. Currently we encode it in the UDP
* checksum, but I guess the tag will be protocol dependent. Also, since the
* tag changes the probe, the user has no direct control of what is sent on
* the wire, since typically a packet is tagged just before sending, after
* scheduling, to maximize the number of probes in flight. Available space
* in the headers is used for tagging, + encoding some information... */
/* XXX hardcoded XXX */
/* 1) Set payload = tag : this is only possible if both the payload and the
* checksum have not been set by the user.
* We need a list of used tags = in flight... + an efficient way to get a
* free one... Also, we need to share tags between several instances ?
* randomized tags ? Also, we need to determine how much size we have to
* encode information. */
if (num_layers < 2 || !(last_layer = probe_get_layer(probe, num_layers - 2))) {
fprintf(stderr, "network_tag_probe: not enough layer (num_layers = %d)\n", (unsigned int)num_layers);
goto ERR_GET_LAYER;
}
// The last layer is the payload, the previous one is the last protocol layer.
// If this layer has a "body" field like icmp, we have no payload and
// we use the body field.
if (last_layer->protocol && protocol_get_field(last_layer->protocol, "body")) {
tag_in_body = true;
}
tag = htons(network_get_available_tag(network));
// Write the tag at offset zero of the payload
if (tag_in_body) {
probe_write_field(probe, "body", &tag, tag_size);
} else {
if (payload_size < tag_size) {
fprintf(stderr, "Payload too short (payload_size = %u tag_size = %u)\n", (unsigned int)payload_size, (unsigned int)tag_size);
goto ERR_INVALID_PAYLOAD;
}
if (!(probe_write_payload(probe, &tag, tag_size))) {
goto ERR_PROBE_WRITE_PAYLOAD;
}
}
// Fix checksum to get a well-formed packet
if (!(probe_update_checksum(probe))) {
fprintf(stderr, "Can't update fields\n");
goto ERR_PROBE_UPDATE_FIELDS;
}
// Retrieve the checksum of UDP/TCP/ICMP checksum (host-side endianness)
if (!(probe_extract_tag(probe, &checksum))) {
fprintf(stderr, "Can't extract tag\n");
goto ERR_PROBE_EXTRACT_CHECKSUM;
}
// Write the probe ID in the UDP/TCP/ICMP checksum
if (!(probe_set_tag(probe, ntohs(tag)))) {
fprintf(stderr, "Can't set tag\n");
goto ERR_PROBE_SET_TAG;
}
// Write the tag using the network-side endianness in the payload
checksum = htons(checksum);
if (tag_in_body) {
if (!(probe_write_field(probe, "body", &checksum, tag_size))) {
fprintf(stderr, "Can't set body\n");
goto ERR_PROBE_SET_FIELD;
}
} else {
if (!probe_write_payload(probe, &checksum, tag_size)) {
fprintf(stderr, "Can't write payload (2)\n");
goto ERR_BUFFER_WRITE_BYTES2;
}
}
return true;
ERR_PROBE_SET_FIELD:
ERR_BUFFER_WRITE_BYTES2:
ERR_PROBE_SET_TAG:
ERR_PROBE_EXTRACT_CHECKSUM:
ERR_PROBE_UPDATE_FIELDS:
ERR_PROBE_WRITE_PAYLOAD:
ERR_INVALID_PAYLOAD:
ERR_GET_LAYER:
return false;
}
