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Message-Id: <20190322183300.196277-10-willemdebruijn.kernel@gmail.com>
Date: Fri, 22 Mar 2019 14:32:56 -0400
From: Willem de Bruijn <willemdebruijn.kernel@...il.com>
To: netdev@...r.kernel.org
Cc: ast@...nel.org, daniel@...earbox.net, sdf@...gle.com,
posk@...gle.com, Willem de Bruijn <willemb@...gle.com>
Subject: [PATCH bpf-next v3 09/13] bpf: add bpf_skb_adjust_room encap flags
From: Willem de Bruijn <willemb@...gle.com>
When pushing tunnel headers, annotate skbs in the same way as tunnel
devices.
For GSO packets, the network stack requires certain fields set to
segment packets with tunnel headers. gro_gse_segment depends on
transport and inner mac header, for instance.
Add an option to pass this information.
Remove the restriction on len_diff to network header length, which
is too short, e.g., for GRE protocols.
Changes
v1->v2:
- document new flags
- BPF_F_ADJ_ROOM_MASK moved
v2->v3:
- BPF_F_ADJ_ROOM_ENCAP_L3_MASK moved
Signed-off-by: Willem de Bruijn <willemb@...gle.com>
---
include/uapi/linux/bpf.h | 16 +++++++++-
net/core/filter.c | 66 +++++++++++++++++++++++++++++++++++++---
2 files changed, 76 insertions(+), 6 deletions(-)
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 4f157d0ec571..837024512baf 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -1486,11 +1486,20 @@ union bpf_attr {
* * **BPF_ADJ_ROOM_NET**: Adjust room at the network layer
* (room space is added or removed below the layer 3 header).
*
- * There is one supported flag at this time:
+ * The following flags are supported at this time:
*
* * **BPF_F_ADJ_ROOM_FIXED_GSO**: Do not adjust gso_size.
* Adjusting mss in this way is not allowed for datagrams.
*
+ * * **BPF_F_ADJ_ROOM_ENCAP_L3_IPV4 **:
+ * * **BPF_F_ADJ_ROOM_ENCAP_L3_IPV6 **:
+ * Any new space is reserved to hold a tunnel header.
+ * Configure skb offsets and other fields accordingly.
+ *
+ * * **BPF_F_ADJ_ROOM_ENCAP_L4_GRE **:
+ * * **BPF_F_ADJ_ROOM_ENCAP_L4_UDP **:
+ * Use with ENCAP_L3 flags to further specify the tunnel type.
+ *
* A call to this helper is susceptible to change the underlaying
* packet buffer. Therefore, at load time, all checks on pointers
* previously done by the verifier are invalidated and must be
@@ -2632,6 +2641,11 @@ enum bpf_func_id {
/* BPF_FUNC_skb_adjust_room flags. */
#define BPF_F_ADJ_ROOM_FIXED_GSO (1ULL << 0)
+#define BPF_F_ADJ_ROOM_ENCAP_L3_IPV4 (1ULL << 1)
+#define BPF_F_ADJ_ROOM_ENCAP_L3_IPV6 (1ULL << 2)
+#define BPF_F_ADJ_ROOM_ENCAP_L4_GRE (1ULL << 3)
+#define BPF_F_ADJ_ROOM_ENCAP_L4_UDP (1ULL << 4)
+
/* Mode for BPF_FUNC_skb_adjust_room helper. */
enum bpf_adj_room_mode {
BPF_ADJ_ROOM_NET,
diff --git a/net/core/filter.c b/net/core/filter.c
index d3240a0a0eeb..c1d19b074d6c 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -2963,11 +2963,20 @@ static u32 bpf_skb_net_base_len(const struct sk_buff *skb)
}
}
-#define BPF_F_ADJ_ROOM_MASK (BPF_F_ADJ_ROOM_FIXED_GSO)
+#define BPF_F_ADJ_ROOM_ENCAP_L3_MASK (BPF_F_ADJ_ROOM_ENCAP_L3_IPV4 | \
+ BPF_F_ADJ_ROOM_ENCAP_L3_IPV6)
+
+#define BPF_F_ADJ_ROOM_MASK (BPF_F_ADJ_ROOM_FIXED_GSO | \
+ BPF_F_ADJ_ROOM_ENCAP_L3_MASK | \
+ BPF_F_ADJ_ROOM_ENCAP_L4_GRE | \
+ BPF_F_ADJ_ROOM_ENCAP_L4_UDP)
static int bpf_skb_net_grow(struct sk_buff *skb, u32 off, u32 len_diff,
u64 flags)
{
+ bool encap = flags & BPF_F_ADJ_ROOM_ENCAP_L3_MASK;
+ unsigned int gso_type = SKB_GSO_DODGY;
+ u16 mac_len, inner_net, inner_trans;
int ret;
if (skb_is_gso(skb) && !skb_is_gso_tcp(skb)) {
@@ -2981,10 +2990,60 @@ static int bpf_skb_net_grow(struct sk_buff *skb, u32 off, u32 len_diff,
if (unlikely(ret < 0))
return ret;
+ if (encap) {
+ if (skb->protocol != htons(ETH_P_IP) &&
+ skb->protocol != htons(ETH_P_IPV6))
+ return -ENOTSUPP;
+
+ if (flags & BPF_F_ADJ_ROOM_ENCAP_L3_IPV4 &&
+ flags & BPF_F_ADJ_ROOM_ENCAP_L3_IPV6)
+ return -EINVAL;
+
+ if (flags & BPF_F_ADJ_ROOM_ENCAP_L4_GRE &&
+ flags & BPF_F_ADJ_ROOM_ENCAP_L4_UDP)
+ return -EINVAL;
+
+ if (skb->encapsulation)
+ return -EALREADY;
+
+ mac_len = skb->network_header - skb->mac_header;
+ inner_net = skb->network_header;
+ inner_trans = skb->transport_header;
+ }
+
ret = bpf_skb_net_hdr_push(skb, off, len_diff);
if (unlikely(ret < 0))
return ret;
+ if (encap) {
+ /* inner mac == inner_net on l3 encap */
+ skb->inner_mac_header = inner_net;
+ skb->inner_network_header = inner_net;
+ skb->inner_transport_header = inner_trans;
+ skb_set_inner_protocol(skb, skb->protocol);
+
+ skb->encapsulation = 1;
+ skb_set_network_header(skb, mac_len);
+
+ if (flags & BPF_F_ADJ_ROOM_ENCAP_L4_UDP)
+ gso_type |= SKB_GSO_UDP_TUNNEL;
+ else if (flags & BPF_F_ADJ_ROOM_ENCAP_L4_GRE)
+ gso_type |= SKB_GSO_GRE;
+ else if (flags & BPF_F_ADJ_ROOM_ENCAP_L3_IPV6)
+ gso_type |= SKB_GSO_IPXIP6;
+ else
+ gso_type |= SKB_GSO_IPXIP4;
+
+ if (flags & BPF_F_ADJ_ROOM_ENCAP_L4_GRE ||
+ flags & BPF_F_ADJ_ROOM_ENCAP_L4_UDP) {
+ int nh_len = flags & BPF_F_ADJ_ROOM_ENCAP_L3_IPV6 ?
+ sizeof(struct ipv6hdr) :
+ sizeof(struct iphdr);
+
+ skb_set_transport_header(skb, mac_len + nh_len);
+ }
+ }
+
if (skb_is_gso(skb)) {
struct skb_shared_info *shinfo = skb_shinfo(skb);
@@ -2993,7 +3052,7 @@ static int bpf_skb_net_grow(struct sk_buff *skb, u32 off, u32 len_diff,
skb_decrease_gso_size(shinfo, len_diff);
/* Header must be checked, and gso_segs recomputed. */
- shinfo->gso_type |= SKB_GSO_DODGY;
+ shinfo->gso_type |= gso_type;
shinfo->gso_segs = 0;
}
@@ -3044,7 +3103,6 @@ static u32 __bpf_skb_max_len(const struct sk_buff *skb)
BPF_CALL_4(bpf_skb_adjust_room, struct sk_buff *, skb, s32, len_diff,
u32, mode, u64, flags)
{
- bool trans_same = skb->transport_header == skb->network_header;
u32 len_cur, len_diff_abs = abs(len_diff);
u32 len_min = bpf_skb_net_base_len(skb);
u32 len_max = __bpf_skb_max_len(skb);
@@ -3073,8 +3131,6 @@ BPF_CALL_4(bpf_skb_adjust_room, struct sk_buff *, skb, s32, len_diff,
}
len_cur = skb->len - skb_network_offset(skb);
- if (skb_transport_header_was_set(skb) && !trans_same)
- len_cur = skb_network_header_len(skb);
if ((shrink && (len_diff_abs >= len_cur ||
len_cur - len_diff_abs < len_min)) ||
(!shrink && (skb->len + len_diff_abs > len_max &&
--
2.21.0.392.gf8f6787159e-goog
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