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authorPetar Penkov <ppenkov@google.com>2018-12-02 20:18:19 -0500
committerDaniel Borkmann <daniel@iogearbox.net>2018-12-03 21:37:51 +0100
commite3da08d057002f9d0831949d51666c3e15dc6b29 (patch)
tree1e7a9ef1d6ad44355a50a26ef15a159fd807c72b /tools
parentlibbpf: Fix license in README.rst (diff)
downloadlinux-dev-e3da08d057002f9d0831949d51666c3e15dc6b29.tar.xz
linux-dev-e3da08d057002f9d0831949d51666c3e15dc6b29.zip
bpf: allow BPF read access to qdisc pkt_len
The pkt_len field in qdisc_skb_cb stores the skb length as it will appear on the wire after segmentation. For byte accounting, this value is more accurate than skb->len. It is computed on entry to the TC layer, so only valid there. Allow read access to this field from BPF tc classifier and action programs. The implementation is analogous to tc_classid, aside from restricting to read access. To distinguish it from skb->len and self-describe export as wire_len. Changes v1->v2 - Rename pkt_len to wire_len Signed-off-by: Petar Penkov <ppenkov@google.com> Signed-off-by: Vlad Dumitrescu <vladum@google.com> Signed-off-by: Willem de Bruijn <willemb@google.com> Acked-by: Song Liu <songliubraving@fb.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Diffstat (limited to 'tools')
-rw-r--r--tools/include/uapi/linux/bpf.h1
-rw-r--r--tools/testing/selftests/bpf/test_verifier.c32
2 files changed, 33 insertions, 0 deletions
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 8050caea7495..0183b8e70a9e 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -2497,6 +2497,7 @@ struct __sk_buff {
__u32 data_meta;
struct bpf_flow_keys *flow_keys;
__u64 tstamp;
+ __u32 wire_len;
};
struct bpf_tunnel_key {
diff --git a/tools/testing/selftests/bpf/test_verifier.c b/tools/testing/selftests/bpf/test_verifier.c
index c3b038f26ece..b4b4a3f93639 100644
--- a/tools/testing/selftests/bpf/test_verifier.c
+++ b/tools/testing/selftests/bpf/test_verifier.c
@@ -14033,6 +14033,38 @@ static struct bpf_test tests[] = {
.result_unpriv = REJECT,
.result = ACCEPT,
},
+ {
+ "check wire_len is not readable by sockets",
+ .insns = {
+ BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_1,
+ offsetof(struct __sk_buff, wire_len)),
+ BPF_EXIT_INSN(),
+ },
+ .errstr = "invalid bpf_context access",
+ .result = REJECT,
+ },
+ {
+ "check wire_len is readable by tc classifier",
+ .insns = {
+ BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_1,
+ offsetof(struct __sk_buff, wire_len)),
+ BPF_EXIT_INSN(),
+ },
+ .prog_type = BPF_PROG_TYPE_SCHED_CLS,
+ .result = ACCEPT,
+ },
+ {
+ "check wire_len is not writable by tc classifier",
+ .insns = {
+ BPF_STX_MEM(BPF_W, BPF_REG_1, BPF_REG_1,
+ offsetof(struct __sk_buff, wire_len)),
+ BPF_EXIT_INSN(),
+ },
+ .prog_type = BPF_PROG_TYPE_SCHED_CLS,
+ .errstr = "invalid bpf_context access",
+ .errstr_unpriv = "R1 leaks addr",
+ .result = REJECT,
+ },
};
static int probe_filter_length(const struct bpf_insn *fp)