add fsseek
diff --git a/src/lib9pclient/seek.c b/src/lib9pclient/seek.c
new file mode 100644
index 0000000..0785c4b
--- /dev/null
+++ b/src/lib9pclient/seek.c
@@ -0,0 +1,46 @@
+#include <u.h>
+#include <libc.h>
+#include <fcall.h>
+#include <9pclient.h>
+#include "fsimpl.h"
+
+vlong
+fsseek(CFid *fid, vlong n, int whence)
+{
+ Dir *d;
+
+ switch(whence){
+ case 0:
+ qlock(&fid->lk);
+ fid->offset = n;
+ qunlock(&fid->lk);
+ break;
+ case 1:
+ qlock(&fid->lk);
+ n += fid->offset;
+ if(n < 0){
+ qunlock(&fid->lk);
+ werrstr("negative offset");
+ return -1;
+ }
+ fid->offset = n;
+ qunlock(&fid->lk);
+ break;
+ case 2:
+ if((d = fsdirfstat(fid)) == nil)
+ return -1;
+ n += d->length;
+ if(n < 0){
+ werrstr("negative offset");
+ return -1;
+ }
+ qlock(&fid->lk);
+ fid->offset = n;
+ qunlock(&fid->lk);
+ break;
+ default:
+ werrstr("bad whence in fsseek");
+ return -1;
+ }
+ return n;
+}
