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bpf: add bpf_skb_adjust_room encap flags

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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@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Willem de Bruijn 2019-03-22 14:32:56 -04:00 committed by Alexei Starovoitov
parent 2278f6cc15
commit 868d523535
2 changed files with 76 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

16
include/uapi/linux/bpf.h
View File

@ -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,

66
net/core/filter.c
View File

@ -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 &&