Date: Sun, 13 Feb 2000 14:46:37 -0800 From: nathan@khmere.com To: "freebsd-net@FreeBSD.ORG" <freebsd-net@FreeBSD.ORG>, "hackers@FreeBSD.ORG" <hackers@FreeBSD.ORG> Subject: Setting the default gw (with c) Message-ID: <38A7344C.71BA918C@khmere.com>
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Greetings !
I have a question, I need to write a small program that sets the default
gw. It is written in C and I have looked at several way to do it. One
way is using ioctl but that way seems a little "old" and not very well
documented. Here is a simple snippet of my code, now when I run it I get
an error "error 22" invalid arg. Does anyone have experience with this
and can point out what I am doing wrong ? I did have it to where it
would work but the kernel never added my netmask to the routing table.
So the route would kinda "hang" their and not do anything. I did tell it
that it was being sent but..... also the flags never where set proper on
the route (when doing route -dvn flush )
Any help would be great ! (oh if this looks familiar, I learned this
from reading both ruote.c and netstat.c. )
struct rt_data_msg{
struct rt_msghdr add_rtm;
union{
struct sockaddr sa;
struct sockaddr_in sin;
struct sockaddr_dl sdl;
}rt_dst, rt_gate, rt_mask;
};
int set_droute(char *gw){
int sockfd, i, err = 0;
int flags = 0, r_addrs = 0;
u_long inits;
char t_gw[32];
register int l;
struct rt_data_msg add_rt;
pid_t pid;
/* check to see if we have a gateway address or quit */
if(!gw){
ERR("set_droute: FREEBSD no route sent ! %d");
return(BAD);
}
else{
/* convet this address if not valid quit */
if((inet_aton(gw, &so_gate.sin.sin_addr)) < 0){
ERR("set_droute: FREEBSD route not valid ! %d");
return(BAD);
}
}
memset(&add_rt, 0, sizeof(struct rt_data_msg));
/* check to see if thier is an existing route or not make an
entry from scratch */
if( (i = get_droute(t_gw)) == BAD){
/* make the address and netmasks */
if((inet_aton("0.0.0.0", &add_rt.rt_mask.sin.sin_addr))
< 0){ err++; }
if((inet_aton("0.0.0.0", &add_rt.rt_dst.sin.sin_addr)) <
0) { err++; }
if((inet_aton(gw, &add_rt.rt_gate.sin.sin_addr)) < 0){
err++; }
if(err > 0){
ERR("get_droute: FREEBSD cannot set mask or dst
or gw invalid addresses %d");
return(BAD);
}
inits = RTV_EXPIRE;
inits |= RTV_RPIPE;
inits |= RTV_SPIPE;
inits |= RTV_SSTHRESH;
r_addrs = RTAX_DST;
r_addrs |= RTAX_GATEWAY;
r_addrs |= RTAX_NETMASK;
flags = RTF_UP;
flags |= RTF_GATEWAY;
flags |= RTF_STATIC;
flags |= RTF_PRCLONING;
/* add thier size */
#define ADD_SIZE(w) l = ROUNDUP(w.sa.sa_len)
#define ROUNDUP(a) ((a) > 0 ? (1 + (((a) - 1) | (sizeof(long) - 1)))
: sizeof(long));
ADD_SIZE(add_rt.rt_dst);
ADD_SIZE(add_rt.rt_gate);
ADD_SIZE(add_rt.rt_mask);
/* add their address family */
#define ADD_FAM(x) x.sin.sin_family = AF_INET;
ADD_FAM(add_rt.rt_dst);
ADD_FAM(add_rt.rt_gate);
ADD_FAM(add_rt.rt_mask);
ADD_FAM(add_rt.rt_genmask);
/* set up all of the flags and tables */
#define RD add_rt.add_rtm
RD.rtm_msglen = l;
RD.rtm_version = RTM_VERSION;
RD.rtm_type = RTM_ADD;
RD.rtm_flags = flags;
RD.rtm_addrs = rtm_addrs;
RD.rtm_inits = RTF_GATEWAY;
RD.rtm_pid = pid = getpid();
RD.rtm_seq = ++SEQ;
if( (sockfd = socket(PF_ROUTE, SOCK_RAW, 0)) < 0){
ERR("set_droute: FREEBSD cannot open socket
%d");
}
/* send it to the kernel */
i = write(sockfd, (char *)&add_rt, l);
syslog(LOG_ERR, "errno = %d ", errno);
}
else{
/* get a buffer for the data */
ERR("get_droute returned ok %d ");
}
return(GOOD);
}
Thank you
nathan
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