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Subject[PATCH] bpf: allow BPF programs access skb_shared_info->gso_segs field
Date
This adds the ability to read gso_segs from a BPF program. This is useful
for user space monitoring systems to get gso_segs statistics for each
arbitrary group of flows defined by the BPF program.

Signed-off-by: Eddie Hao <eddieh@google.com>
---
include/uapi/linux/bpf.h | 1 +
net/core/filter.c | 9 +++++++++
2 files changed, 10 insertions(+)

diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index b7db3261c62d..282085445616 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -2266,6 +2266,7 @@ struct __sk_buff {
/* ... here. */

__u32 data_meta;
+ unsigned short gso_segs;
};

struct bpf_tunnel_key {
diff --git a/net/core/filter.c b/net/core/filter.c
index b9ec916f4e3a..f17e249f3fbb 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -5820,6 +5820,15 @@ static u32 bpf_convert_ctx_access(enum bpf_access_type type,
bpf_target_off(struct sock_common,
skc_num, 2, target_size));
break;
+
+ case offsetof(struct __sk_buff, gso_segs):
+ BUILD_BUG_ON(FIELD_SIZEOF(struct skb_shared_info, gso_segs) !=
+ sizeof(unsigned short));
+ off = offsetof(struct sk_buff, end);
+ off += offsetof(struct skb_shared_info, gso_segs);
+ *insn++ = BPF_LDX_MEM(BPF_SIZEOF(unsigned short), si->dst_reg,
+ si->src_reg, off);
+ break;
}

return insn - insn_buf;
--
2.18.0.203.gfac676dfb9-goog
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