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Fix: Derive the exclude_rt from the preferred route #649

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May 24, 2023
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Fix: Derive the exclude_rt from the preferred route #649

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58 changes: 35 additions & 23 deletions programs/ziti-edge-tunnel/netif_driver/linux/tun.c
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Original file line number Diff line number Diff line change
Expand Up @@ -329,38 +329,50 @@ static void init_dns_maintainer(uv_loop_t *loop, const char *tun_name, uint32_t
}

static int tun_exclude_rt(netif_handle dev, uv_loop_t *l, const char *addr) {
char def_route[128];
FILE *def_rt = popen("ip route show default", "r");
if (def_rt == NULL) {
ZITI_LOG(WARN, "ip route cmd failed[%d:%s]", errno, strerror(errno));
return -1;
char cmd[1024];
char route[128];
FILE *cmdpipe = NULL;
int n;

n = snprintf(cmd, sizeof cmd,
"ip -o route show match %s table all | "
"awk '/dev %s/ { next; } { if (match($0, / metric ([^ ]+)/)) { metric = substr($0, RSTART, RLENGTH); } printf \"%%s %%s%%s\\n\", $2, $3, metric; }'",
addr, dev->name);
if (n > 0 && (size_t) n < sizeof cmd) {
ZITI_LOG(DEBUG, "popen(%s)", cmd);
cmdpipe = popen(cmd, "r");
} else {
errno = ENOMEM;
}
int def_rt_size = (int)fread(def_route, 1, sizeof(def_route), def_rt);

// only look at first line
char *p = strchr(def_route, '\n');
if (p != NULL) {
*p = 0;
if (cmdpipe == NULL) {
ZITI_LOG(WARN, "ip route cmd popen(%s) failed [%d:%s]", cmd, errno, strerror(errno));
return -1;
}

ZITI_LOG(DEBUG, "default route is '%.*s'", def_rt_size, def_route);
pclose(def_rt);
errno = 0;
size_t size = fread(route, 1, sizeof route, cmdpipe);
int saved_errno = errno;
int ferr = ferror(cmdpipe);
(void) pclose(cmdpipe);
if (ferr) {
errno = saved_errno ? saved_errno : EIO;
ZITI_LOG(WARN, "ip route cmd I/O failed [%d:%s]", errno, strerror(errno));
return -1;
}

const char *type = NULL;
if ((p = strstr(def_route, "via ")) != NULL) {
type = "via";
} else if ((p = strstr(def_route, "dev ")) != NULL) {
type = "dev";
} else {
ZITI_LOG(WARN, "could not find default route");
// only look at first line
char *p = memchr(route, '\n', size);
// was a full line read?
if (p == NULL || p == route) {
ZITI_LOG(WARN, "failed to retrieve destination route");
return -1;
}
*p = 0;

char *gw = p + 4;
char *endgw = strchr(gw, ' ');
int gw_len = (int)(endgw - gw);
ZITI_LOG(DEBUG, "route is %s %s", addr, route);

return run_command("ip route replace %s %s %.*s", addr, type, gw_len, gw);
return run_command("ip route replace %s %s", addr, route);
}

netif_driver tun_open(uv_loop_t *loop, uint32_t tun_ip, uint32_t dns_ip, const char *dns_block, char *error, size_t error_len) {
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