struct packet *new_udp_packet(int address_family,
enum direction_t direction,
u16 udp_payload_bytes,
char **error)
{
struct packet *packet = NULL; /* the newly-allocated result packet */
struct header *udp_header = NULL; /* the UDP header info */
/* Calculate lengths in bytes of all sections of the packet */
const int ip_option_bytes = 0;
const int ip_header_bytes = (ip_header_min_len(address_family) +
ip_option_bytes);
const int udp_header_bytes = sizeof(struct udp);
const int ip_bytes =
ip_header_bytes + udp_header_bytes + udp_payload_bytes;
/* Sanity-check all the various lengths */
if (ip_option_bytes & 0x3) {
asprintf(error, "IP options are not padded correctly "
"to ensure IP header is a multiple of 4 bytes: "
"%d excess bytes", ip_option_bytes & 0x3);
return NULL;
}
assert((udp_header_bytes & 0x3) == 0);
assert((ip_header_bytes & 0x3) == 0);
if (ip_bytes > MAX_UDP_DATAGRAM_BYTES) {
asprintf(error, "UDP datagram too large");
return NULL;
}
/* Allocate and zero out a packet object of the desired size */
packet = packet_new(ip_bytes);
memset(packet->buffer, 0, ip_bytes);
packet->direction = direction;
packet->flags = 0;
packet->ecn = ECN_NONE;
/* Set IP header fields */
set_packet_ip_header(packet, address_family, ip_bytes,
packet->ecn, IPPROTO_UDP);
udp_header = packet_append_header(packet, HEADER_UDP,
sizeof(struct udp));
udp_header->total_bytes = udp_header_bytes + udp_payload_bytes;
/* Find the start of UDP section of the packet */
packet->udp = (struct udp *) (ip_start(packet) + ip_header_bytes);
/* Set UDP header fields */
packet->udp->src_port = htons(0);
packet->udp->dst_port = htons(0);
packet->udp->len = htons(udp_header_bytes + udp_payload_bytes);
packet->udp->check = 0;
packet->ip_bytes = ip_bytes;
return packet;
}
struct packet *new_tcp_packet(int socket_fd,
int address_family,
enum direction_t direction,
enum ip_ecn_t ecn,
const char *flags,
u32 start_sequence,
u16 tcp_payload_bytes,
u32 ack_sequence,
s32 window,
const struct tcp_options *tcp_options,
char **error)
{
struct packet *packet = NULL; /* the newly-allocated result packet */
/* Calculate lengths in bytes of all sections of the packet */
const int ip_option_bytes = 0;
const int tcp_option_bytes = tcp_options ? tcp_options->length : 0;
const int ip_header_bytes = (ip_header_len(address_family) +
ip_option_bytes);
const int tcp_header_bytes = sizeof(struct tcp) + tcp_option_bytes;
const int ip_bytes =
ip_header_bytes + tcp_header_bytes + tcp_payload_bytes;
/* Sanity-check all the various lengths */
if (ip_option_bytes & 0x3) {
asprintf(error, "IP options are not padded correctly "
"to ensure IP header is a multiple of 4 bytes: "
"%d excess bytes", ip_option_bytes & 0x3);
printf("1\n");
return NULL;
}
if (tcp_option_bytes & 0x3) {
asprintf(error,
"TCP options are not padded correctly "
"to ensure TCP header is a multiple of 4 bytes: "
"%d excess bytes", tcp_option_bytes & 0x3);
printf("2\n");
return NULL;
}
assert((tcp_header_bytes & 0x3) == 0);
assert((ip_header_bytes & 0x3) == 0);
if (tcp_header_bytes > MAX_TCP_HEADER_BYTES) {
asprintf(error, "TCP header too large");
return NULL;
}
if (ip_bytes > MAX_TCP_DATAGRAM_BYTES) {
asprintf(error, "TCP segment too large");
return NULL;
}
if (!is_tcp_flags_spec_valid(flags, error)){
return NULL;
}
/* Allocate and zero out a packet object of the desired size */
packet = packet_new(ip_bytes);
memset(packet->buffer, 0, ip_bytes);
packet->ip_bytes = ip_bytes;
packet->direction = direction;
packet->socket_script_fd = socket_fd;
packet->flags = 0;
packet->ecn = ecn;
/* Set IP header fields */
set_packet_ip_header(packet, address_family, ip_bytes, direction, ecn,
IPPROTO_TCP);
/* Find the start of TCP sections of the packet */
packet->tcp = (struct tcp *) (packet_start(packet) + ip_header_bytes);
u8 *tcp_option_start = (u8 *) (packet->tcp + 1);
/* Set TCP header fields */
packet->tcp->src_port = htons(0);
packet->tcp->dst_port = htons(0);
packet->tcp->seq = htonl(start_sequence);
packet->tcp->ack_seq = htonl(ack_sequence);
packet->tcp->doff = tcp_header_bytes / 4;
if (window == -1) {
if (direction == DIRECTION_INBOUND) {
asprintf(error, "window must be specified"
" for inbound packets");
return NULL;
}
packet->tcp->window = 0;
packet->flags |= FLAG_WIN_NOCHECK;
} else {
packet->tcp->window = htons(window);
}
packet->tcp->check = 0;
packet->tcp->urg_ptr = 0;
packet->tcp->fin = is_tcp_flag_set('F', flags);
packet->tcp->syn = is_tcp_flag_set('S', flags);
packet->tcp->rst = is_tcp_flag_set('R', flags);
packet->tcp->psh = is_tcp_flag_set('P', flags);
packet->tcp->ack = is_tcp_flag_set('.', flags);
packet->tcp->urg = 0;
packet->tcp->ece = is_tcp_flag_set('E', flags);
packet->tcp->cwr = is_tcp_flag_set('W', flags);
if (tcp_options == NULL) {
packet->flags |= FLAG_OPTIONS_NOCHECK;
} else if (tcp_options->length > 0) {
/* Copy TCP options into packet */
memcpy(tcp_option_start, tcp_options->data,
tcp_options->length);
}
return packet;
}
struct packet *new_icmp_packet(int address_family,
enum direction_t direction,
const char *type_string,
const char *code_string,
int protocol,
u32 tcp_start_sequence,
u32 payload_bytes,
s64 mtu,
char **error)
{
s32 type = -1; /* bad type; means "unknown so far" */
s32 code = -1; /* bad code; means "unknown so far" */
struct packet *packet = NULL; /* the newly-allocated result packet */
/* Calculate lengths in bytes of all sections of the packet.
* For now we only support the most common ICMP message
* format, which includes at the end the original outgoing IP
* header and the first 8 bytes after that (which will
* typically have the port info needed to demux the message).
*/
const int ip_fixed_bytes = ip_header_len(address_family);
const int ip_option_bytes = 0;
const int ip_header_bytes = ip_fixed_bytes + ip_option_bytes;
const int echoed_bytes = ip_fixed_bytes + ICMP_ECHO_BYTES;
const int icmp_bytes = icmp_header_len(address_family) + echoed_bytes;
const int ip_bytes = ip_header_bytes + icmp_bytes;
/* Sanity-check all the various lengths */
if (ip_option_bytes & 0x3) {
asprintf(error, "IP options are not padded correctly "
"to ensure IP header is a multiple of 4 bytes: "
"%d excess bytes", ip_option_bytes & 0x3);
goto error_out;
}
assert((ip_header_bytes & 0x3) == 0);
/* Parse the ICMP type and code */
if (parse_icmp_type_and_code(address_family, type_string, code_string,
&type, &code, error))
goto error_out;
assert(is_valid_u8(type));
assert(is_valid_u8(code));
/* Allocate and zero out a packet object of the desired size */
packet = packet_new(ip_bytes);
memset(packet->buffer, 0, ip_bytes);
packet->ip_bytes = ip_bytes;
packet->direction = direction;
packet->flags = 0;
packet->ecn = 0;
/* Set IP header fields */
const enum ip_ecn_t ecn = ECN_NONE;
set_packet_ip_header(packet, address_family, ip_bytes, direction, ecn,
icmp_protocol(address_family));
/* Find the start of the ICMP header and then populate common fields. */
void *icmp_header = packet_start(packet) + ip_header_bytes;
if (set_packet_icmp_header(packet, icmp_header, address_family,
type, code, mtu, error))
goto error_out;
/* All ICMP message types currently supported by this tool
* include a copy of the outbound IP header and the first few
* bytes inside. To ensure that the inbound ICMP message gets
* demuxed to the correct socket in the kernel, here we
* construct enough of a basic IP header and during test
* execution we fill in the port numbers and (if specified)
* TCP sequence number in the TCP header.
*/
u8 *echoed_ip = packet_echoed_ip_header(packet);
const int echoed_ip_bytes = (ip_fixed_bytes +
layer4_header_len(protocol) +
payload_bytes);
set_ip_header(echoed_ip, address_family, echoed_ip_bytes,
reverse_direction(direction), ecn, protocol);
if (protocol == IPPROTO_TCP) {
u32 *seq = packet_echoed_tcp_seq(packet);
*seq = htonl(tcp_start_sequence);
}
return packet;
error_out:
if (packet != NULL)
packet_free(packet);
return NULL;
}
