diff options
Diffstat (limited to 'test/packetdrill/tcp_packet.c')
| -rw-r--r-- | test/packetdrill/tcp_packet.c | 166 |
1 files changed, 166 insertions, 0 deletions
diff --git a/test/packetdrill/tcp_packet.c b/test/packetdrill/tcp_packet.c new file mode 100644 index 0000000..aa667b6 --- /dev/null +++ b/test/packetdrill/tcp_packet.c @@ -0,0 +1,166 @@ +/* + * Copyright 2013 Google Inc. + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public License + * as published by the Free Software Foundation; either version 2 + * of the License, or (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, write to the Free Software + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA + * 02110-1301, USA. + */ +/* + * Author: ncardwell@google.com (Neal Cardwell) + * + * Implementation for module for formatting TCP packets. + */ + +#include "tcp_packet.h" + +#include "ip_packet.h" +#include "tcp.h" + +/* The full list of valid TCP bit flag characters */ +static const char valid_tcp_flags[] = "FSRP.EWCU"; + +/* Are all the TCP flags in the given string valid? */ +static bool is_tcp_flags_spec_valid(const char *flags, char **error) +{ + const char *s; + + for (s = flags; *s != '\0'; ++s) { + if (!strchr(valid_tcp_flags, *s)) { + asprintf(error, "Invalid TCP flag: '%c'", *s); + return false; + } + } + return true; +} + +/* Parse tcpdump-style ASCII representation of flags to look for a flag */ +static inline int is_tcp_flag_set(char flag, const char *flags) +{ + return (strchr(flags, flag) != NULL) ? 1 : 0; +} + +struct packet *new_tcp_packet(int address_family, + enum direction_t direction, + struct ip_info ip_info, + u16 src_port, + u16 dst_port, + const char *flags, + u32 start_sequence, + u16 tcp_payload_bytes, + u32 ack_sequence, + s32 window, + u16 urg_ptr, + const struct tcp_options *tcp_options, + char **error) +{ + struct packet *packet = NULL; /* the newly-allocated result packet */ + struct header *tcp_header = NULL; /* the TCP header info */ + /* 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_min_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); + 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); + 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->direction = direction; + packet->flags = 0; + packet->tos_chk = ip_info.tos.check; + + /* Set IP header fields */ + set_packet_ip_header(packet, address_family, ip_bytes, + ip_info.tos.value, ip_info.flow_label, + ip_info.ttl, IPPROTO_TCP); + + tcp_header = packet_append_header(packet, HEADER_TCP, tcp_header_bytes); + tcp_header->total_bytes = tcp_header_bytes + tcp_payload_bytes; + + /* Find the start of TCP sections of the packet */ + packet->tcp = (struct tcp *) (ip_start(packet) + ip_header_bytes); + u8 *tcp_option_start = (u8 *) (packet->tcp + 1); + + /* Set TCP header fields */ + packet->tcp->src_port = htons(src_port); + packet->tcp->dst_port = htons(dst_port); + 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 = htons(urg_ptr); + 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 = is_tcp_flag_set('U', flags); + 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); + } + + packet->ip_bytes = ip_bytes; + return packet; +} |