[PATCH net-next 3/5] ebpf: Add sg_filter_run()

[Tushar Dave <tushar.n.dave@oracle.com>]

When sg_filter_run() is invoked it runs the attached eBPF
prog of type BPF_PROG_TYPE_SOCKET_SG_FILTER which deals with
struct scatterlist.

Signed-off-by: Tushar Dave <tushar.n.dave@oracle.com>
Acked-by: Sowmini Varadhan <sowmini.varadhan@oracle.com>
---
 include/linux/filter.h         |  8 ++++++++
 include/uapi/linux/bpf.h       |  6 ++++++
 net/core/filter.c              | 35 +++++++++++++++++++++++++++++++++++
 tools/include/uapi/linux/bpf.h |  6 ++++++
 4 files changed, 55 insertions(+)

diff --git a/include/linux/filter.h b/include/linux/filter.h
index 6791a0a..ae664a9 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -1113,4 +1113,12 @@ struct bpf_sock_ops_kern {
 					 */
 };
 
+enum __socksg_action {
+	__SOCKSG_PASS = 0,
+	__SOCKSG_DROP,
+	__SOCKSG_REDIRECT,
+};
+
+int sg_filter_run(struct sock *sk, struct scatterlist *sg);
+
 #endif /* __LINUX_FILTER_H__ */
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 6ec1e32..1e11789 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -2428,6 +2428,12 @@ enum sk_action {
 	SK_PASS,
 };
 
+enum socksg_action {
+	SOCKSG_PASS = 0,
+	SOCKSG_DROP,
+	SOCKSG_REDIRECT,
+};
+
 /* user accessible metadata for SK_MSG packet hook, new fields must
  * be added to the end of this structure
  */
diff --git a/net/core/filter.c b/net/core/filter.c
index 469c488..a3afc61 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -121,6 +121,41 @@ int sk_filter_trim_cap(struct sock *sk, struct sk_buff *skb, unsigned int cap)
 }
 EXPORT_SYMBOL(sk_filter_trim_cap);
 
+int sg_filter_run(struct sock *sk, struct scatterlist *sg)
+{
+	struct sk_filter *filter;
+	int result = 0;
+
+	if (!sg)
+		return result;
+
+	rcu_read_lock();
+	filter = rcu_dereference(sk->sk_filter);
+	if (filter) {
+		struct sk_msg_buff mb = {0};
+
+		memcpy(mb.sg_data, sg, sizeof(*sg) * MAX_SKB_FRAGS);
+		mb.sg_start = 0;
+		mb.sg_end = sg_nents(sg);
+		mb.data = sg_virt(sg);
+		mb.data_end = mb.data + sg->length;
+		mb.sg_copy[mb.sg_end - 1] = true;
+
+		result = BPF_PROG_RUN(filter->prog, &mb);
+
+		/* BPF prog may have changed mb.sg_data e.g. may linearize
+		 * multiple scatterlist entries into one. Therefore, make sure
+		 * to update original sg and mark the sg end.
+		 */
+		memcpy(sg, mb.sg_data, sizeof(*sg) * MAX_SKB_FRAGS);
+		sg_mark_end(&sg[mb.sg_end - 1]);
+	}
+	rcu_read_unlock();
+
+	return result;
+}
+EXPORT_SYMBOL(sg_filter_run);
+
 BPF_CALL_1(bpf_skb_get_pay_offset, struct sk_buff *, skb)
 {
 	return skb_get_poff(skb);
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 6ec1e32..1e11789 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -2428,6 +2428,12 @@ enum sk_action {
 	SK_PASS,
 };
 
+enum socksg_action {
+	SOCKSG_PASS = 0,
+	SOCKSG_DROP,
+	SOCKSG_REDIRECT,
+};
+
 /* user accessible metadata for SK_MSG packet hook, new fields must
  * be added to the end of this structure
  */
-- 
1.8.3.1