ref: e0fdebf39443a01e4cd4378099cc59001719df18
dir: /sys/src/libndb/dnsquery.c/
#include <u.h> #include <libc.h> #include <bio.h> #include <ndb.h> #include <ndbhf.h> #include <ip.h> static Ndbtuple *doquery(int, char *dn, char *type); /* * search for a tuple that has the given 'attr=val' and also 'rattr=x'. * copy 'x' into 'buf' and return the whole tuple. * * return nil if not found. */ Ndbtuple* dnsquery(char *net, char *val, char *type) { char buf[128]; Ndbtuple *t; int fd; /* if the address is V4 or V6 null address, give up early */ if(strcmp(val, "::") == 0 || strcmp(val, "0.0.0.0") == 0) return nil; if(net == nil) net = "/net"; snprint(buf, sizeof(buf), "%s/dns", net); if((fd = open(buf, ORDWR|OCEXEC)) < 0) return nil; /* zero out the error string */ werrstr(""); /* if this is a reverse lookup, first lookup the domain name */ if(strcmp(type, "ptr") == 0){ mkptrname(val, buf, sizeof buf); t = doquery(fd, buf, "ptr"); } else t = doquery(fd, val, type); /* * TODO: make fd static and keep it open to reduce 9P traffic * walking to /net*^/dns. */ close(fd); ndbsetmalloctag(t, getcallerpc(&net)); return t; } static Ndbtuple* doquery(int fd, char *dn, char *type) { char buf[1024]; int n; Ndbtuple *t, *first, *last; snprint(buf, sizeof(buf), "!%s %s", dn, type); if(write(fd, buf, strlen(buf)) < 0) return nil; seek(fd, 0, 0); first = last = nil; for(;;){ n = read(fd, buf, sizeof(buf)-2); if(n <= 0) break; if(buf[n-1] != '\n') buf[n++] = '\n'; /* ndbparsline needs a trailing new line */ buf[n] = 0; /* check for the error condition */ if(buf[0] == '!'){ werrstr("%s", buf+1); return nil; } t = _ndbparseline(buf); if(t != nil){ if(first != nil) last->entry = t; else first = t; last = t; while(last->entry != nil) last = last->entry; } } return first; }