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authorLawrence Brakmo <brakmo@fb.com>2017-12-01 10:15:04 -0800
committerDaniel Borkmann <daniel@iogearbox.net>2017-12-05 14:55:32 +0100
commitf19397a5c65665d66e3866b42056f1f58b7a366b (patch)
treef9633a9c7a0df69155c36b4e92692e909dbb417f
parent792f3dd6f02b25afc0b42adce2efd523e81c3fb1 (diff)
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bpf: Add access to snd_cwnd and others in sock_ops
Adds read access to snd_cwnd and srtt_us fields of tcp_sock. Since these fields are only valid if the socket associated with the sock_ops program call is a full socket, the field is_fullsock is also added to the bpf_sock_ops struct. If the socket is not a full socket, reading these fields returns 0. Note that in most cases it will not be necessary to check is_fullsock to know if there is a full socket. The context of the call, as specified by the 'op' field, can sometimes determine whether there is a full socket. The struct bpf_sock_ops has the following fields added: __u32 is_fullsock; /* Some TCP fields are only valid if * there is a full socket. If not, the * fields read as zero. */ __u32 snd_cwnd; __u32 srtt_us; /* Averaged RTT << 3 in usecs */ There is a new macro, SOCK_OPS_GET_TCP32(NAME), to make it easier to add read access to more 32 bit tcp_sock fields. Signed-off-by: Lawrence Brakmo <brakmo@fb.com> Acked-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
-rw-r--r--include/linux/filter.h1
-rw-r--r--include/net/tcp.h6
-rw-r--r--include/uapi/linux/bpf.h6
-rw-r--r--net/core/filter.c36
4 files changed, 47 insertions, 2 deletions
diff --git a/include/linux/filter.h b/include/linux/filter.h
index 80b5b482cb46..0062302e1285 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -985,6 +985,7 @@ struct bpf_sock_ops_kern {
u32 reply;
u32 replylong[4];
};
+ u32 is_fullsock;
};
#endif /* __LINUX_FILTER_H__ */
diff --git a/include/net/tcp.h b/include/net/tcp.h
index 4e09398009c1..89a656077884 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -2012,10 +2012,12 @@ static inline int tcp_call_bpf(struct sock *sk, int op)
struct bpf_sock_ops_kern sock_ops;
int ret;
- if (sk_fullsock(sk))
+ memset(&sock_ops, 0, sizeof(sock_ops));
+ if (sk_fullsock(sk)) {
+ sock_ops.is_fullsock = 1;
sock_owned_by_me(sk);
+ }
- memset(&sock_ops, 0, sizeof(sock_ops));
sock_ops.sk = sk;
sock_ops.op = op;
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 4c223ab30293..80d62e88590c 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -941,6 +941,12 @@ struct bpf_sock_ops {
__u32 local_ip6[4]; /* Stored in network byte order */
__u32 remote_port; /* Stored in network byte order */
__u32 local_port; /* stored in host byte order */
+ __u32 is_fullsock; /* Some TCP fields are only valid if
+ * there is a full socket. If not, the
+ * fields read as zero.
+ */
+ __u32 snd_cwnd;
+ __u32 srtt_us; /* Averaged RTT << 3 in usecs */
};
/* List of known BPF sock_ops operators.
diff --git a/net/core/filter.c b/net/core/filter.c
index 4d644ad17457..754abe1041b7 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -4437,6 +4437,42 @@ static u32 sock_ops_convert_ctx_access(enum bpf_access_type type,
*insn++ = BPF_LDX_MEM(BPF_H, si->dst_reg, si->dst_reg,
offsetof(struct sock_common, skc_num));
break;
+
+ case offsetof(struct bpf_sock_ops, is_fullsock):
+ *insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(
+ struct bpf_sock_ops_kern,
+ is_fullsock),
+ si->dst_reg, si->src_reg,
+ offsetof(struct bpf_sock_ops_kern,
+ is_fullsock));
+ break;
+
+/* Helper macro for adding read access to tcp_sock fields. */
+#define SOCK_OPS_GET_TCP32(FIELD_NAME) \
+ do { \
+ BUILD_BUG_ON(FIELD_SIZEOF(struct tcp_sock, FIELD_NAME) != 4); \
+ *insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF( \
+ struct bpf_sock_ops_kern, \
+ is_fullsock), \
+ si->dst_reg, si->src_reg, \
+ offsetof(struct bpf_sock_ops_kern, \
+ is_fullsock)); \
+ *insn++ = BPF_JMP_IMM(BPF_JEQ, si->dst_reg, 0, 2); \
+ *insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF( \
+ struct bpf_sock_ops_kern, sk),\
+ si->dst_reg, si->src_reg, \
+ offsetof(struct bpf_sock_ops_kern, sk));\
+ *insn++ = BPF_LDX_MEM(BPF_W, si->dst_reg, si->dst_reg, \
+ offsetof(struct tcp_sock, FIELD_NAME)); \
+ } while (0)
+
+ case offsetof(struct bpf_sock_ops, snd_cwnd):
+ SOCK_OPS_GET_TCP32(snd_cwnd);
+ break;
+
+ case offsetof(struct bpf_sock_ops, srtt_us):
+ SOCK_OPS_GET_TCP32(srtt_us);
+ break;
}
return insn - insn_buf;
}