/* mkcap.c * A small program to generate the ASCII form of a capture with TCP * segments of a reasonable nature. The payload is all zeros. * * $Id: mkcap.c,v 1.2 2003/10/05 14:58:11 sharpe Exp $ * * By Ronnie Sahlberg and Richard Sharpe. From a program initially * written by Ronnie. * Copyright 2003 Ronnie Sahlberg and Richard Sharpe * * 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., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. * * Using it to generate a capture file: * ./mkcap [some-flags] > some-file * text2pcap [some-other-flags] some-file some-file.cap * For example: ./mkcap -a 2500 -s 15 -I "02 03 04 05" -i "45 45 45 45" -P "00 14" > ftp.cap.asci text2pcap -t "%Y/%m/%d%t%H:%M:%S." ftp.cap.asci ftp.cap */ #include #include #include #define ETH_1 "00 00 9c fa 1d 74" #define ETH_2 "00 1a b8 93 f6 71" #define IP_1 "0a 01 01 17" #define IP_2 "0a 01 01 ea" #define PORT_1 "01 00" #define PORT_2 "10 00" char *eth_1 = ETH_1; char *eth_2 = ETH_2; char *ip_1 = IP_1; char *ip_2 = IP_2; char *port_1 = PORT_1; char *port_2 = PORT_2; int verbose = 0; typedef enum { normal = 0, random_ack_drop = 1, random_data_drop = 2, } run_type_t; typedef struct { int drop_seg_start; int drop_seg_count; } seg_drop_t; /* * The array of which segments should be dropped ... */ seg_drop_t *drops = NULL; int seg_drop_count = 0; /* The array of which ACKs should be dropped. This is complicated because * An ack might not be generated for a segment because of delayed ACKs. */ seg_drop_t *ack_drops = NULL; int ack_drop_count = 0; int total_bytes = 32768; int run_type = 0; int seq_2=0; int seq_1=0; int ts=0; int jitter = 0; int send_spacing = 10; int ack_delay = 5000; int tcp_nodelay = 0; int tcp_delay_time = 1000; /* What is the real time here? */ /* * If tcp_nodelay is set, then this is the amount of data left ... */ int remaining_data = 0; int snap_len = 1500; int window = 32768; int ssthresh = 16384; int cwnd = 1460; int used_win = 0; int segment = 0; #define SEG_ACK_LOST 1 #define SEG_SEG_LOST 2 struct seg_hist_s { int seq_num; /* First sequence number in segment */ int len; /* Number of bytes in segment */ int ts; /* Timestamp when sent */ int seg_num; /* Segment number sent. This can change */ /* but a retransmit will have a new seg */ int flags; /* Flags as above for ack and seg loss */ int acks_first_seq; /* How many times we have seen an ack for the first seq number in this seg */ }; #define SEG_HIST_SIZE 128 struct seg_hist_s seg_hist[128]; /* This should be dynamic */ int next_slot = 0; int first_slot = 0; int delayed_ack = 1; /* Default is delayed ACKs in use ... */ int delayed_ack_wait = 30000; /* 30 mS before an ACK is generated if */ /* no other traffic */ void makeseg(char *eth1, char *eth2, char *ip1, char *ip2, char *p1, char *p2, int *s1, int *s2, char *flags, int len) { int i; printf("2002/01/07 00:00:%02d.%06d\n", ts/1000000, ts%1000000); printf("0000 %s %s 08 00\n", eth1, eth2); printf("000e 45 00 %02x %02x 00 00 00 00 40 06 00 00 %s %s\n", (len+40)>>8, (len+40)&0xff, ip1, ip2); printf("0022 %s %s %02x %02x %02x %02x %02x %02x %02x %02x 50 %s 80 00 00 00 00 00", p1, p2, ((*s1)>>24)&0xff, ((*s1)>>16)&0xff, ((*s1)>>8)&0xff, ((*s1))&0xff, ((*s2)>>24)&0xff, ((*s2)>>16)&0xff, ((*s2)>>8)&0xff, ((*s2))&0xff, flags ); for(i=0;i<(len<(snap_len-40)?len:snap_len-40);i++)printf(" 00"); printf("\n"); printf("\n"); (*s1)+=len; } /* * Figure out when the next ack is due ... here we must skip the acks for * frames that are marked as ACKs dropped as well as the frames marked as * frames dropped. These will be marked by the routine that generates ACKs. * Returns a timestamp value. Returns 2^^31-1 if none are due at all */ int next_ack_due() { int slot = next_slot; int ack_lost = 0, seg_lost = 0; if (next_slot == first_slot) return (((unsigned int)(1<<31)) - 1); /* * Figure out if we need to issue an ACK. We skip all outstanding packets * that are marked as ack lost or packet lost. * * We would not usually come in here with a frame marked as lost or ack lost * rather, we will come in here and specify that the ack was due at a * certain time, and gen_next_ack would then determine that the ack * should be lost or the packet lost. */ /* * Look for a seg slot that is not lost or dropped */ while (seg_hist[slot].flags & (SEG_ACK_LOST || SEG_SEG_LOST)) { if (seg_hist[slot].flags & SEG_ACK_LOST) ack_lost++; if (seg_hist[slot].flags & SEG_SEG_LOST) seg_lost++; slot = (slot + 1) % SEG_HIST_SIZE; } if (slot == next_slot) return (((unsigned int)(1<<31)) - 1); /* * If there is only one slot occupied, or a segment was lost then * an ACK is due after the last [good] segment left plus ack_delay */ if (slot == first_slot && next_slot == ((first_slot + 1) % SEG_HIST_SIZE)) return (seg_hist[first_slot].ts + ack_delay + jitter); if (seg_lost) return (seg_hist[slot].ts + ack_delay + jitter); /* * OK, now, either we have only seen lost acks, or there are more than * one outstanding segments, so figure out when the ACK is due. * * If delayed ACK is in force, ACK is due after every second seg, but * if we had a lost ack, then we must ignore 2*lost_ack segments. So, * if there has not been that many segments sent, we return infinity * as the next ACK time */ if (ack_lost) { if (delayed_ack) { if (((first_slot + 1 + 2 * ack_lost) % SEG_HIST_SIZE) >= next_slot) /* XXX: FIXME, what about when the window is closed */ /* XXX: FIXME, use the correct value for this */ return (((unsigned int)(1<<31)) - 1); else return seg_hist[(first_slot + 1 + 2 * ack_lost) % SEG_HIST_SIZE].ts + ack_delay + jitter; } else return seg_hist[slot].ts + ack_delay + jitter; } else { if (delayed_ack) return (seg_hist[(first_slot + 1)%SEG_HIST_SIZE].ts+ack_delay+jitter); else return (seg_hist[first_slot].ts+ack_delay+jitter); } } /* * Update the relevant info of the sent seg */ add_seg_sent(int seq, int len) { /* * Should check we have not wrapped around and run into the unacked * stuff ... */ /*if (next_slot == first_slot) ;*/ segment++; seg_hist[next_slot].seq_num = seq; seg_hist[next_slot].len = len; seg_hist[next_slot].ts = ts; seg_hist[next_slot].seg_num = segment; seg_hist[next_slot].flags = 0; seg_hist[next_slot].acks_first_seq = 0; used_win = used_win + len; /* Update the window used */ /* * Now, update next_slot ... */ next_slot = (next_slot + 1) % SEG_HIST_SIZE; } /* * Generate the next ack based on the above reasoning ... */ #define NO_FORCE_ACK 0 #define FORCE_ACK 1 /* * Generate the next ACK. If we did not generate an ACK, return 0, * else return 1. */ int gen_next_ack(int force, int spacing) { int seq_to_ack, new_ts, data_acked; /* * We need to check if the segment that we are about to generate an * ack for is a segment that should be dropped ... or an ack that should * be dropped. * * Figure out what we are doing before freeing segments ... */ seq_to_ack = seg_hist[first_slot].seq_num + seg_hist[first_slot].len; used_win = used_win - seg_hist[first_slot].len; data_acked = seg_hist[first_slot].len; new_ts = seg_hist[first_slot].ts + ack_delay; first_slot = (first_slot + 1) % SEG_HIST_SIZE; /* * If delayed ACK in force, then ACK the next segment if there is one */ if (delayed_ack && (first_slot != next_slot)) { seq_to_ack += seg_hist[first_slot].len; used_win = used_win - seg_hist[first_slot].len; data_acked += seg_hist[first_slot].len; new_ts = seg_hist[first_slot].ts + ack_delay; first_slot = (first_slot + 1) % SEG_HIST_SIZE; } /* * We don't want time to go backward ... */ if (new_ts + jitter <= ts) ts++; else ts = new_ts + jitter; jitter = (rand() % 10 - 5); /* Update jitter ... */ makeseg(eth_2, eth_1, ip_2, ip_1, port_2, port_1, &seq_2, &seq_to_ack, "10", 0); /* * Do we want the exponential part or the linear part? */ if (cwnd >= ssthresh) cwnd += (1460*data_acked)/cwnd; /* is this right? */ else cwnd = cwnd + data_acked; if (verbose) fprintf(stderr, "Ack rcvd. ts: %d, data_acked: %d, cwnd: %d, window: %d\n", ts, data_acked, cwnd, window); if (cwnd > window) cwnd = window; } void makeackedrun(int len, int spacing, int ackdelay) { int old_seq1, next_ack_ts=0; if (verbose) fprintf(stderr, "makeackedrun: Len=%d, spacing=%d, ackdelay=%d\n", len, spacing, ackdelay); old_seq1=seq_1; while(len>0){ /* * Each time we output a segment, we should check to see if an * ack is due back before the next segment is due ... */ int seglen, saved_seq; seglen=(len>1460)?1460:len; /* * Only output what is left in the cwnd. * We assume there is space in the congestion window here */ if (seglen > (cwnd - used_win)) seglen = cwnd - used_win; len-=seglen; saved_seq = seq_1; if (verbose) fprintf(stderr, "Sending segment. ts: %d, jitter: %d\n", ts, jitter); if(len){ makeseg(eth_1, eth_2, ip_1, ip_2, port_1, port_2, &seq_1, &seq_2, "10", seglen); } else { makeseg(eth_1, eth_2, ip_1, ip_2, port_1, port_2, &seq_1, &seq_2, "18", seglen); } add_seg_sent(saved_seq, seglen); /* * Now, if the window is closed, then we have to eject an * ack, otherwise we can eject more data. * Also, the other end will tend to ack two segments at * a time ... and that ack might fall between two * outgoing segments */ jitter = (rand()%10) - 5; /* What if spacing too small */ if (verbose) fprintf(stderr, "used win: %d, cwnd: %d\n", used_win, cwnd); if ((next_ack_ts = next_ack_due()) < ts + spacing + jitter) { int old_ts = ts; /* * Generate the ack and retire the segments * If delayed ACK in use, there should be two * or more outstanding segments ... */ if (verbose) fprintf(stderr, "Non forced ACK ...ts + spacing + jitter:%d, jitter: %d\n", ts + spacing + jitter, jitter); gen_next_ack(NO_FORCE_ACK, spacing); /* * We don't want time to go backwards ... */ if (old_ts + spacing + jitter <= ts) ts++; else ts = old_ts + spacing + jitter; } else if (used_win == cwnd) { /* * We need an ACK, so generate it and retire the * segments and advance the ts to the time of the ack */ if (verbose) fprintf(stderr, "Forced ACK ... \n"); gen_next_ack(FORCE_ACK, spacing); ts+=(spacing+jitter); /* Should not use spacing here */ } else { ts+=(spacing+jitter); } if (verbose) fprintf(stderr, "Next Ack Due: %d\n", next_ack_ts); } } void makeackedrundroppedtail8kb(int len, int spacing, int ackdelay) { int old_seq1; int dropped_tail; int i; int num_dupes; if (verbose) fprintf(stderr, "makeackedrundroppedtail8kB: Len=%d, spacing=%d, ackdelay=%d\n", len, spacing, ackdelay); old_seq1=seq_1; while(len>0){ int seglen; seglen=(len>1460)?1460:len; len-=seglen; if(seglen==1460){ makeseg(eth_1, eth_2, ip_1, ip_2, port_1, port_2, &seq_1, &seq_2, "10", seglen); } else { makeseg(eth_1, eth_2, ip_1, ip_2, port_1, port_2, &seq_1, &seq_2, "18", seglen); } ts+=spacing; } ts+=ackdelay; i=0; num_dupes=-1; dropped_tail=0; while(old_seq1!=seq_1){ int ack_len; ack_len=((seq_1-old_seq1)>2920)?2920:(seq_1-old_seq1); i++; if(i==6){ dropped_tail=old_seq1; } old_seq1+=ack_len; if(i<6){ makeseg(eth_2, eth_1, ip_2, ip_1, port_2, port_1, &seq_2, &old_seq1, "10", 0); } else if (i==6) { makeseg(eth_2, eth_1, ip_2, ip_1, port_2, port_1, &seq_2, &dropped_tail, "10", 0); num_dupes+=2; } else { makeseg(eth_2, eth_1, ip_2, ip_1, port_2, port_1, &seq_2, &dropped_tail, "10", 0); makeseg(eth_2, eth_1, ip_2, ip_1, port_2, port_1, &seq_2, &dropped_tail, "10", 0); num_dupes+=2; } ts+=spacing/2; } if(!dropped_tail){ return; } if(num_dupes<3){ int seglen; int new_seq; ts+=1000000; seglen=((seq_1-dropped_tail)>1460)?1460:(seq_1-dropped_tail); if(seglen==1460){ makeseg(eth_1, eth_2, ip_1, ip_2, port_1, port_2, &dropped_tail, &seq_2, "10", seglen); } else { makeseg(eth_1, eth_2, ip_1, ip_2, port_1, port_2, &dropped_tail, &seq_2, "18", seglen); } ts+=ackdelay; new_seq=seglen+seq_1; makeseg(eth_2, eth_1, ip_2, ip_1, port_2, port_1, &seq_2, &seq_1, "10", 0); ts+=spacing; return; } while(dropped_tail!=seq_1){ int seglen; int ack; seglen=((seq_1-dropped_tail)>1460)?1460:(seq_1-dropped_tail); if(seglen==1460){ makeseg(eth_1, eth_2, ip_1, ip_2, port_1, port_2, &dropped_tail, &seq_2, "10", seglen); } else { makeseg(eth_1, eth_2, ip_1, ip_2, port_1, port_2, &dropped_tail, &seq_2, "18", seglen); } ts+=ackdelay; ack=dropped_tail; makeseg(eth_2, eth_1, ip_2, ip_1, port_2, port_1, &seq_2, &ack, "10", 0); ts+=spacing; } } void usage() { fprintf(stderr, "Usage: mkcap [OPTIONS], where\n"); fprintf(stderr, "\t-a is the delay to an ACK (RTT)\n"); fprintf(stderr, "\t-b is the bytes to send on connection\n"); fprintf(stderr, "\t-i is the sender IP address in hex\n"); fprintf(stderr, "\t-I is the recipient IP address in hex\n"); fprintf(stderr, "\t-n is almost the ISN for the sender\n"); fprintf(stderr, "\t-N is almost the ISN for the recipient\n"); fprintf(stderr, "\t-p is the port number for sender\n"); fprintf(stderr, "\t-P is the port number for recipient\n"); fprintf(stderr, "\t-s is the send spacing\n"); fprintf(stderr, "\t-w is the window size\n"); } int all_digits(char *str) { int i; if (!str || !(*str)) { return 0; } for (i = 0; str[i]; i++) { if (!isdigit(str[i])) return 0; } return 1; } /* * Process a list of drops. These are of the form: * * first_seg,seg_count[,first_seg,seg_count]* */ void process_drop_list(char *drop_list) { int commas=0, i; char *tok, *save; if (!drop_list || !(*drop_list)) { fprintf(stderr, "Strange drop list. NULL or an empty string. No drops!\n"); return; } save = (char *)strdup(drop_list); for (tok=(char *)strtok(drop_list, ","); tok; tok=(char *)strtok(NULL, ",")) { commas++; } /* Now, we have commas, divide by two and round up */ seg_drop_count = (commas+1)/2; drops = (seg_drop_t *)malloc(sizeof(seg_drop_t) * seg_drop_count); if (!drops) { fprintf(stderr, "Unable to allocate space for drops ... going without!\n"); seg_drop_count = 0; free(save); return; } /* Now, go through the list again and build the drop list. Any errors and */ /* we abort and print a usage message */ commas = 0; for (tok=(char *)strtok(save, ","); tok; tok=(char *)strtok(NULL, ",")) { int num = atoi(tok); if (!all_digits(tok)) { fprintf(stderr, "Error in segment offset or count. Not all digits: %s\n", tok); fprintf(stderr, "No packet drops being performed!\n"); free(save); free(drops); seg_drop_count = 0; drops = NULL; return; } if (num == 0) num = 1; if (commas % 2) drops[commas / 2].drop_seg_count = num; else drops[commas / 2].drop_seg_start = num; } } int main(int argc, char *argv[]) { int i; int len; int type; int cnt; extern char *optarg; extern int optind; int opt; while ((opt = getopt(argc, argv, "a:b:d:Di:I:j:l:n:N:p:P:r:s:vw:")) != EOF) { switch (opt) { case 'a': ack_delay = atoi(optarg); break; case 'b': /* Bytes ... */ total_bytes = atoi(optarg); break; case 'd': /* A list of drops to simulate */ process_drop_list(optarg); break; case 'D': /* Toggle tcp_nodelay */ tcp_nodelay = (tcp_nodelay + 1) % 1; break; case 'i': ip_1 = optarg; break; case 'I': ip_2 = optarg; break; case 'l': snap_len = atoi(optarg); break; case 'n': /* ISN for send dirn, ie, seq_1 */ seq_1 = atoi(optarg); break; case 'N': /* ISN for recv dirn, ie, seq_2 */ seq_2 = atoi(optarg); break; case 'p': port_1 = optarg; break; case 'P': port_2 = optarg; break; case 'r': run_type = atoi(optarg); break; case 's': send_spacing = atoi(optarg); break; case 'v': verbose++; break; case 'w': /* Window ... */ window = atoi(optarg); ssthresh = window / 2; /* Have to recalc this ... */ break; default: usage(); break; } } if (verbose) fprintf(stderr, "IP1: %s, IP2: %s, P1: %s, P2: %s, Ack Delay: %d, Send Spacing: %d\n", ip_1, ip_2, port_1, port_2, ack_delay, send_spacing); /*return 0; */ if (run_type == 0) { makeackedrun(total_bytes, send_spacing, ack_delay); } else { for(cnt=0;cnt<200;cnt++){ type=rand()%150; if(type<75){ int j; j=5+rand()%10; for(i=0;i