[RFC PATCH 13/16] bpf/crib: Add CRIB kfuncs for restoring data in skb

[Juntong Deng]

This patch adds CRIB kfuncs for restoring data in skb.

bpf_restore_skb_rcv_queue() is used to create a new skb based on
the previously dumped skb information and add it to the tail of
the specified receive queue.

bpf_restore_skb_data() is used to restore data in the skb and
must be used after bpf_restore_skb_rcv_queue().

Signed-off-by: Juntong Deng <juntong.deng@xxxxxxxxxxx>
---
 include/linux/bpf_crib.h      | 13 +++++++
 kernel/bpf/crib/bpf_crib.c    |  3 ++
 kernel/bpf/crib/bpf_restore.c | 67 +++++++++++++++++++++++++++++++++++
 3 files changed, 83 insertions(+)

diff --git a/include/linux/bpf_crib.h b/include/linux/bpf_crib.h
index c073166e60a0..5b7d44642f80 100644
--- a/include/linux/bpf_crib.h
+++ b/include/linux/bpf_crib.h
@@ -46,4 +46,17 @@ struct bpf_iter_skb_data_kern {
 	unsigned int chunklen;
 } __aligned(8);
 
+struct bpf_crib_skb_info {
+	int headerlen;
+	int len;
+	int size;
+	int tstamp;
+	int dev_scratch;
+	int protocol;
+	int csum;
+	int transport_header;
+	int network_header;
+	int mac_header;
+} __aligned(8);
+
 #endif /* _BPF_CRIB_H */
diff --git a/kernel/bpf/crib/bpf_crib.c b/kernel/bpf/crib/bpf_crib.c
index 462ae1ab50e5..beada526021a 100644
--- a/kernel/bpf/crib/bpf_crib.c
+++ b/kernel/bpf/crib/bpf_crib.c
@@ -300,6 +300,9 @@ BTF_ID_FLAGS(func, bpf_iter_skb_data_get_chunk_len, KF_ITER_GETTER)
 BTF_ID_FLAGS(func, bpf_iter_skb_data_get_offset, KF_ITER_GETTER)
 BTF_ID_FLAGS(func, bpf_iter_skb_data_destroy, KF_ITER_DESTROY)
 
+BTF_ID_FLAGS(func, bpf_restore_skb_rcv_queue, KF_ACQUIRE | KF_TRUSTED_ARGS | KF_RET_NULL)
+BTF_ID_FLAGS(func, bpf_restore_skb_data, KF_TRUSTED_ARGS)
+
 BTF_KFUNCS_END(bpf_crib_kfuncs)
 
 static int bpf_prog_run_crib(struct bpf_prog *prog,
diff --git a/kernel/bpf/crib/bpf_restore.c b/kernel/bpf/crib/bpf_restore.c
index 6bbb4b01e34b..7966c02e416e 100644
--- a/kernel/bpf/crib/bpf_restore.c
+++ b/kernel/bpf/crib/bpf_restore.c
@@ -7,7 +7,74 @@
  */
 
 #include <linux/bpf_crib.h>
+#include <linux/skbuff.h>
+#include <net/sock.h>
+
+extern struct sk_buff *bpf_skb_acquire(struct sk_buff *skb);
 
 __bpf_kfunc_start_defs();
 
+/**
+ * bpf_restore_skb_rcv_queue() - Create a new skb based on the previously
+ * dumped skb information and add it to the tail of the specified queue to
+ * achieve restoring the skb
+ *
+ * Note that this function acquires a reference to struct sk_buff.
+ *
+ * @head: queue that needs to restore the skb
+ * @sk: struct sock where the queue is located.
+ * @skb_info: previously dumped skb information
+ *
+ * @returns a pointer to the skb if the restoration of the skb
+ * was successful, otherwise returns NULL.
+ */
+__bpf_kfunc struct sk_buff *
+bpf_restore_skb_rcv_queue(struct sk_buff_head *head, struct sock *sk,
+			  struct bpf_crib_skb_info *skb_info)
+{
+	struct sk_buff *skb;
+
+	skb = alloc_skb(skb_info->size, GFP_KERNEL);
+	if (!skb)
+		return NULL;
+
+	skb_reserve(skb, skb_info->headerlen);
+	skb_put(skb, skb_info->len);
+
+	skb->tstamp = skb_info->tstamp;
+	skb->dev_scratch = skb_info->dev_scratch;
+	skb->protocol = skb_info->protocol;
+	skb->csum = skb_info->csum;
+	skb->transport_header = skb_info->transport_header;
+	skb->network_header = skb_info->network_header;
+	skb->mac_header = skb_info->mac_header;
+
+	lock_sock(sk);
+	skb_queue_tail(head, skb);
+	skb_set_owner_r(skb, sk);
+	release_sock(sk);
+
+	return bpf_skb_acquire(skb);
+}
+
+/**
+ * bpf_restore_skb_data() - Restore the data in skb
+ *
+ * @skb: skb that needs to restore data
+ * @offset: data offset in skb
+ * @data: data buffer
+ * @len: data length
+ *
+ * @returns the number of bytes of data restored if
+ * the restoration was successful, otherwise returns -1.
+ */
+__bpf_kfunc int bpf_restore_skb_data(struct sk_buff *skb, int offset, char *data, int len)
+{
+	if (offset + len > skb_headroom(skb) + skb->len)
+		return -1;
+
+	memcpy(skb->head + offset, data, len);
+	return len;
+}
+
 __bpf_kfunc_end_defs();
-- 
2.39.2