Date: Mon, 23 Dec 1996 15:19:42 +1100 (EST) From: Julian Assange <proff@iq.org> To: danny@panda.hilink.com.au (Daniel O'Callaghan) Cc: hackers@freebsd.org Subject: Re: ipretard.c selective tcp/ip queues and throughput limiters Message-ID: <199612230419.PAA03748@profane.iq.org> In-Reply-To: <Pine.BSF.3.91.961223091538.229V-100000@panda.hilink.com.au> from Daniel O'Callaghan at "Dec 23, 96 09:16:35 am"
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Written this morning. If people find it useful, I'll polish it.
example:
# ipfw add divert 92 tcp from any to any 80 out via ed0
# ./ipretard -v -t 1000/300 -w 2208
/* ipretard (c) 1996 Julian Assange (proff@suburbia.net) All Rights Reserved */
#include <stdio.h>
#include <stdlib.h>
#include <sys/time.h>
#include <sys/types.h>
#include <sys/uio.h>
#include <unistd.h>
#include <string.h>
#include <fcntl.h>
#include <signal.h>
#include <errno.h>
#include <sys/socket.h>
#include <netinet/in_systm.h>
#include <netinet/in.h>
#include <netinet/ip.h>
#include <netinet/tcp.h>
#define MAX_IP (65535+100)
#define MAX_PACKET (MAX_IP+sizeof(struct packet)-1)
struct packet {
struct packet *next, *prev;
time_t time;
int len;
struct sockaddr_in in;
char data[1];
};
int holdoff_write=0;
int holdoffs=0;
int delay_drops=0;
int window_changes=0;
int bytes_in=0;
int bytes_out=0;
int add_bytes_out=0;
int packets_in=0;
int packets_out=0;
int packets_queued=0;
int bytes_queued=0;
double samples=60.0*5.0; /* 5 minute period */
double max_thru=0.0;
double load_avg;
time_t ti;
int verbose=0;
void
sigalrm(int i)
{
if (max_thru!=0.0) {
load_avg=load_avg*(1.0-1.0/samples)+add_bytes_out/samples;
if (load_avg>max_thru) {
holdoff_write = 1;
holdoffs++;
} else
holdoff_write = 0;
}
bytes_out+=add_bytes_out;
add_bytes_out=0;
if (verbose)
printf("in: %d/%d %d avg out: %d/%d %d avg queued: %d/%d drop: %d win_change: %d holdoffs: %d loadavg %.2f\n", bytes_in, packets_in, packets_in? bytes_in/packets_in: 0, bytes_out, packets_out, packets_out? bytes_out/packets_out: 0, bytes_queued, packets_queued, delay_drops, window_changes, holdoffs, load_avg);
ti=time(NULL);
#ifdef POSIX
signal(SIGALRM, sigalrm);
#endif
alarm(1);
}
u_short
fast_ip_gen_check(struct ip *ip) /* well, for C anyway.. */
{
register u_short *u = (u_short *)ip;
register int sum = 0;
u_char hl = ip->ip_hl * 4;
sum += *u++;
sum += *u++;
sum += *u++;
sum += *u++;
sum += *u++;
u++; /* skip checksum */
sum += *u++;
sum += *u++;
sum += *u++;
sum += *u++;
if (hl != sizeof (*ip))
for (hl = (hl - sizeof (*ip)) / 2; hl--;)
sum += *u++;
sum = (sum >> 16) + (sum & 0xffff); /* fold carries */
return (u_short) ~sum;
}
u_short
fast_tcp_gen_check(struct ip *ip) /* well, for C anyway.. */
{
register u_short *u;
register int sum = 0;
u_short len = ntohs(ip->ip_len) - ip->ip_hl * 4;
u_char resprot[2] =
{0, IPPROTO_TCP};
u = (u_short *) &ip->ip_src;
sum += *u++;
sum += *u++;
sum += *u++;
sum += *u++;
sum += *(u_short *) resprot;
sum += htons(len);
u = (u_short *) ((char*)ip + ip->ip_hl * 4);
sum += *u++;
sum += *u++;
sum += *u++;
sum += *u++;
sum += *u++;
sum += *u++;
sum += *u++;
sum += *u++;
u++; /* skip th_sum */
sum += *u++;
if (!(len -= sizeof (struct tcphdr)))
goto plainhdr;
for (; len > 15; len -= 16) {
sum += *u++;
sum += *u++;
sum += *u++;
sum += *u++;
sum += *u++;
sum += *u++;
sum += *u++;
sum += *u++;
}
for (; len > 1; len -= 2)
sum += *u++;
if (len == 1)
sum += *(u_char *) u;
plainhdr:
sum = (sum >> 16) + (sum & 0xffff); /* fold carries */
len = ~sum;
return len;
}
void
usage(char *av0)
{
fprintf(stderr, "usage: %s [-b ring_buf_len][-d max_packet_delay][-p divert_port][-t max_throughput_per_sec/sample_period][-v][-w max_window]\n", av0);
exit(1);
}
int
main(int argc, char **argv)
{
int c;
int fd;
int div_port=92;
int buf_len=256*1024; /* 256k */
struct sockaddr_in in;
fd_set fdr_set, fdw_set;
int max_window=0;
int max_ring_delay=5;
struct packet *pq_base, *pq_head=NULL, *pq_tail;
while ((c=getopt(argc, argv, "b:d:p:t:vw:"))!=-1)
switch(c)
{
case 'b':
buf_len=atoi(optarg);
if (buf_len<MAX_PACKET) {
fprintf(stderr, "%s: buf_len must be at least %d bytes\n", argv[0], MAX_PACKET);
exit(1);
}
break;
case 'd':
max_ring_delay=atoi(optarg);
break;
case 'p':
div_port=atoi(optarg);
break;
case 't':
{
char *p=strchr(optarg, '/');
if (!p) {
fprintf(stderr, "%s: -m requires max_throughput/period e.g -m 5000/600 is 5k/s average measured over a 10 minute period\n", argv[0]);
usage(argv[0]);
}
*p++='\0';
max_thru=atof(optarg);
samples=atoi(p);
}
case 'v':
verbose++;
break;
case 'w':
max_window=atoi(optarg);
break;
default:
usage(argv[0]);
}
if ((fd=socket(PF_INET, SOCK_RAW, IPPROTO_DIVERT))<0) {
perror("socket");
exit(1);
}
memset(&in, 0, sizeof in);
in.sin_family=PF_INET;
in.sin_port=htons(div_port);
if (bind(fd, (struct sockaddr *)&in, sizeof in)!=0) {
perror("bind");
exit(1);
}
if (!(pq_tail=pq_base=malloc(buf_len))) {
perror("malloc");
exit(1);
}
fcntl(fd, F_SETFL, O_NONBLOCK|fcntl(fd, F_GETFL, 0));
memset(pq_tail, 0, sizeof *pq_tail);
FD_ZERO(&fdr_set);
FD_ZERO(&fdw_set);
signal(SIGALRM, sigalrm);
alarm(1);
ti=time(NULL);
for (;;) {
int n;
if (bytes_queued<buf_len-MAX_PACKET-sizeof(struct packet))
FD_SET(fd, &fdr_set);
else
FD_CLR(fd, &fdr_set);
if (!holdoff_write && pq_head)
FD_SET(fd, &fdw_set);
else
FD_CLR(fd, &fdw_set);
n=select(fd+1, &fdr_set, &fdw_set, NULL, NULL);
if (n==0)
continue;
if (n<0) {
if (errno==EINTR)
continue;
perror("select");
exit(1);
}
if (FD_ISSET(fd, &fdr_set)) {
int cc;
int in_len=sizeof(struct sockaddr_in);
while ((cc=recvfrom(fd, pq_tail->data, MAX_IP, 0, (struct sockaddr*)&pq_tail->in, &in_len))>0) {
struct packet *pq;
pq_tail->len=cc;
pq_tail->time=ti;
bytes_queued+=sizeof(struct packet)-1+cc;
bytes_in+=cc;
if ((pq=(char*)pq_tail+sizeof(struct packet)-1+cc)+MAX_PACKET>(char *)pq_base+buf_len)
pq=pq_base;
if (!pq_head)
pq_head=pq_tail;
if (pq_tail->prev)
pq_tail->prev->next=pq_tail;
pq->next=NULL;
pq->prev=pq_tail;
pq_tail=pq;
packets_queued++;
packets_in++;
}
}
if (packets_queued && FD_ISSET(fd, &fdw_set)) {
if (ti-pq_head->time > max_ring_delay) {
delay_drops++;
goto deqeue;
}
if (max_window &&
pq_head->len>=sizeof(struct ip)+sizeof(struct tcphdr)) {
struct ip *ip=(struct ip*)pq_head->data;
u_short len=ntohs(ip->ip_len);
if (ip->ip_p==IPPROTO_TCP && len==pq_head->len) {
struct tcphdr *tcp=(struct tcphdr*)((char*)ip+ip->ip_hl*4);
if (ntohs(tcp->th_win)>max_window) {
tcp->th_win=htons(max_window);
tcp->th_sum=fast_tcp_gen_check(ip);
window_changes++;
}
}
}
/* according to divert(4) diverts to incoming
need a valid ip_sum, while outgoing diverts
have their ip_sum recalculated by the ip stack */
if (pq_head->in.sin_addr.s_addr!=INADDR_ANY) {
struct ip *ip=(struct ip*)pq_head->data;
ip->ip_sum=fast_ip_gen_check(ip);
}
if (sendto(fd, pq_head->data, pq_head->len, 0, (struct sockaddr*)&pq_head->in, sizeof(pq_head->in))==pq_head->len) {
packets_out++;
add_bytes_out+=pq_head->len;
deqeue:
bytes_queued-=sizeof(struct packet)-1+pq_head->len;
pq_head=pq_head->next;
if (pq_head)
pq_head->prev=NULL;
packets_queued--;
} else {
switch (errno) {
case EAGAIN:
case ENOBUFS:
continue;
case EMSGSIZE:
default:
perror("sendto");
goto deqeue;
}
}
}
}
exit(1);
}
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