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Message-Id: <20181108151137.3975-1-nicolas.dichtel@6wind.com>
Date: Thu, 8 Nov 2018 16:11:37 +0100
From: Nicolas Dichtel <nicolas.dichtel@...nd.com>
To: ast@...nel.org, daniel@...earbox.net, davem@...emloft.net
Cc: netdev@...r.kernel.org, Nicolas Dichtel <nicolas.dichtel@...nd.com>
Subject: [PATCH bpf-next] filter: add BPF_ADJ_ROOM_DATA mode to bpf_skb_adjust_room()
This new mode enables to add or remove an l2 header in a programmatic way
with cls_bpf.
For example, it enables to play with mpls headers.
Signed-off-by: Nicolas Dichtel <nicolas.dichtel@...nd.com>
---
include/uapi/linux/bpf.h | 3 ++
net/core/filter.c | 54 ++++++++++++++++++++++++++++++++++
tools/include/uapi/linux/bpf.h | 3 ++
3 files changed, 60 insertions(+)
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 852dc17ab47a..47407fd5162b 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -1467,6 +1467,8 @@ union bpf_attr {
*
* * **BPF_ADJ_ROOM_NET**: Adjust room at the network layer
* (room space is added or removed below the layer 3 header).
+ * * **BPF_ADJ_ROOM_DATA**: Adjust room at the beginning of the
+ * packet (room space is added or removed below skb->data).
*
* All values for *flags* are reserved for future usage, and must
* be left at zero.
@@ -2408,6 +2410,7 @@ enum bpf_func_id {
/* Mode for BPF_FUNC_skb_adjust_room helper. */
enum bpf_adj_room_mode {
BPF_ADJ_ROOM_NET,
+ BPF_ADJ_ROOM_DATA,
};
/* Mode for BPF_FUNC_skb_load_bytes_relative helper. */
diff --git a/net/core/filter.c b/net/core/filter.c
index e521c5ebc7d1..e699849b269d 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -2884,6 +2884,58 @@ static int bpf_skb_adjust_net(struct sk_buff *skb, s32 len_diff)
return ret;
}
+static int bpf_skb_data_shrink(struct sk_buff *skb, u32 len)
+{
+ unsigned short hhlen = skb->dev->header_ops ?
+ skb->dev->hard_header_len : 0;
+ int ret;
+
+ ret = skb_unclone(skb, GFP_ATOMIC);
+ if (unlikely(ret < 0))
+ return ret;
+
+ __skb_pull(skb, len);
+ skb_reset_mac_header(skb);
+ skb_reset_network_header(skb);
+ skb->network_header += hhlen;
+ skb_reset_transport_header(skb);
+ return 0;
+}
+
+static int bpf_skb_data_grow(struct sk_buff *skb, u32 len)
+{
+ unsigned short hhlen = skb->dev->header_ops ?
+ skb->dev->hard_header_len : 0;
+ int ret;
+
+ ret = skb_cow(skb, len);
+ if (unlikely(ret < 0))
+ return ret;
+
+ skb_push(skb, len);
+ skb_reset_mac_header(skb);
+ return 0;
+}
+
+static int bpf_skb_adjust_data(struct sk_buff *skb, s32 len_diff)
+{
+ u32 len_diff_abs = abs(len_diff);
+ bool shrink = len_diff < 0;
+ int ret;
+
+ if (unlikely(len_diff_abs > 0xfffU))
+ return -EFAULT;
+
+ if (shrink && len_diff_abs >= skb_headlen(skb))
+ return -EFAULT;
+
+ ret = shrink ? bpf_skb_data_shrink(skb, len_diff_abs) :
+ bpf_skb_data_grow(skb, len_diff_abs);
+
+ bpf_compute_data_pointers(skb);
+ return ret;
+}
+
BPF_CALL_4(bpf_skb_adjust_room, struct sk_buff *, skb, s32, len_diff,
u32, mode, u64, flags)
{
@@ -2891,6 +2943,8 @@ BPF_CALL_4(bpf_skb_adjust_room, struct sk_buff *, skb, s32, len_diff,
return -EINVAL;
if (likely(mode == BPF_ADJ_ROOM_NET))
return bpf_skb_adjust_net(skb, len_diff);
+ if (likely(mode == BPF_ADJ_ROOM_DATA))
+ return bpf_skb_adjust_data(skb, len_diff);
return -ENOTSUPP;
}
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 852dc17ab47a..47407fd5162b 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -1467,6 +1467,8 @@ union bpf_attr {
*
* * **BPF_ADJ_ROOM_NET**: Adjust room at the network layer
* (room space is added or removed below the layer 3 header).
+ * * **BPF_ADJ_ROOM_DATA**: Adjust room at the beginning of the
+ * packet (room space is added or removed below skb->data).
*
* All values for *flags* are reserved for future usage, and must
* be left at zero.
@@ -2408,6 +2410,7 @@ enum bpf_func_id {
/* Mode for BPF_FUNC_skb_adjust_room helper. */
enum bpf_adj_room_mode {
BPF_ADJ_ROOM_NET,
+ BPF_ADJ_ROOM_DATA,
};
/* Mode for BPF_FUNC_skb_load_bytes_relative helper. */
--
2.18.0
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