filter: Allow to create sk-unattached filters

Today, BPF filters are bind to sockets. Since BPF machine becomes handy
for other purposes, this patch allows to create unattached filter.

Signed-off-by: Jiri Pirko <jpirko@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/linux/filter.h b/include/linux/filter.h
index 8eeb205..92dd993 100644 (file)
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -153,6 +153,9 @@ static inline unsigned int sk_filter_len(const struct sk_filter *fp)
 extern int sk_filter(struct sock *sk, struct sk_buff *skb);
 extern unsigned int sk_run_filter(const struct sk_buff *skb,
                                  const struct sock_filter *filter);
+extern int sk_unattached_filter_create(struct sk_filter **pfp,
+                                      struct sock_fprog *fprog);
+extern void sk_unattached_filter_destroy(struct sk_filter *fp);
 extern int sk_attach_filter(struct sock_fprog *fprog, struct sock *sk);
 extern int sk_detach_filter(struct sock *sk);
 extern int sk_chk_filter(struct sock_filter *filter, unsigned int flen);

diff --git a/net/core/filter.c b/net/core/filter.c
index 5dea452..cfbea88 100644 (file)
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -587,6 +587,67 @@ void sk_filter_release_rcu(struct rcu_head *rcu)
 }
 EXPORT_SYMBOL(sk_filter_release_rcu);
 
+static int __sk_prepare_filter(struct sk_filter *fp)
+{
+       int err;
+
+       fp->bpf_func = sk_run_filter;
+
+       err = sk_chk_filter(fp->insns, fp->len);
+       if (err)
+               return err;
+
+       bpf_jit_compile(fp);
+       return 0;
+}
+
+/**
+ *     sk_unattached_filter_create - create an unattached filter
+ *     @fprog: the filter program
+ *     @sk: the socket to use
+ *
+ * Create a filter independent ofr any socket. We first run some
+ * sanity checks on it to make sure it does not explode on us later.
+ * If an error occurs or there is insufficient memory for the filter
+ * a negative errno code is returned. On success the return is zero.
+ */
+int sk_unattached_filter_create(struct sk_filter **pfp,
+                               struct sock_fprog *fprog)
+{
+       struct sk_filter *fp;
+       unsigned int fsize = sizeof(struct sock_filter) * fprog->len;
+       int err;
+
+       /* Make sure new filter is there and in the right amounts. */
+       if (fprog->filter == NULL)
+               return -EINVAL;
+
+       fp = kmalloc(fsize + sizeof(*fp), GFP_KERNEL);
+       if (!fp)
+               return -ENOMEM;
+       memcpy(fp->insns, fprog->filter, fsize);
+
+       atomic_set(&fp->refcnt, 1);
+       fp->len = fprog->len;
+
+       err = __sk_prepare_filter(fp);
+       if (err)
+               goto free_mem;
+
+       *pfp = fp;
+       return 0;
+free_mem:
+       kfree(fp);
+       return err;
+}
+EXPORT_SYMBOL_GPL(sk_unattached_filter_create);
+
+void sk_unattached_filter_destroy(struct sk_filter *fp)
+{
+       sk_filter_release(fp);
+}
+EXPORT_SYMBOL_GPL(sk_unattached_filter_destroy);
+
 /**
  *     sk_attach_filter - attach a socket filter
  *     @fprog: the filter program
@@ -617,16 +678,13 @@ int sk_attach_filter(struct sock_fprog *fprog, struct sock *sk)
 
        atomic_set(&fp->refcnt, 1);
        fp->len = fprog->len;
-       fp->bpf_func = sk_run_filter;
 
-       err = sk_chk_filter(fp->insns, fp->len);
+       err = __sk_prepare_filter(fp);
        if (err) {
                sk_filter_uncharge(sk, fp);
                return err;
        }
 
-       bpf_jit_compile(fp);
-
        old_fp = rcu_dereference_protected(sk->sk_filter,
                                           sock_owned_by_user(sk));
        rcu_assign_pointer(sk->sk_filter, fp);