On 7/12/21 9:10 PM, Yonghong Song wrote:
On 7/12/21 10:28 AM, John Fastabend wrote:
Yonghong Song wrote:
libbpf is used as a submodule in bcc.
When importing latest libbpf repo in bcc, I observed the
following compilation errors when compiling on ubuntu 16.04.
.../netlink.c:416:23: error: ‘TC_H_CLSACT’ undeclared (first use in this function)
*parent = TC_H_MAKE(TC_H_CLSACT,
^
.../netlink.c:418:9: error: ‘TC_H_MIN_INGRESS’ undeclared (first use in this function)
TC_H_MIN_INGRESS : TC_H_MIN_EGRESS);
^
.../netlink.c:418:28: error: ‘TC_H_MIN_EGRESS’ undeclared (first use in this function)
TC_H_MIN_INGRESS : TC_H_MIN_EGRESS);
^
.../netlink.c: In function ‘__get_tc_info’:
.../netlink.c:522:11: error: ‘TCA_BPF_ID’ undeclared (first use in this function)
if (!tbb[TCA_BPF_ID])
^
In ubuntu 16.04, TCA_BPF_* enumerator looks like below
enum {
TCA_BPF_UNSPEC,
TCA_BPF_ACT,
...
TCA_BPF_NAME,
TCA_BPF_FLAGS,
__TCA_BPF_MAX,
};
#define TCA_BPF_MAX (__TCA_BPF_MAX - 1)
while in latest bpf-next, the enumerator looks like
enum {
TCA_BPF_UNSPEC,
...
TCA_BPF_FLAGS,
TCA_BPF_FLAGS_GEN,
TCA_BPF_TAG,
TCA_BPF_ID,
__TCA_BPF_MAX,
};
In this patch, TCA_BPF_ID is defined as a macro with proper value and this
works regardless of whether TCA_BPF_ID is defined in uapi header or not.
I also added a comparison "TCA_BPF_MAX < TCA_BPF_ID" in function __get_tc_info()
such that if the compare result if true, returns -EOPNOTSUPP. This is used to
prevent otherwise array overflows:
.../netlink.c:538:10: warning: array subscript is above array bounds [-Warray-bounds]
if (!tbb[TCA_BPF_ID])
^
Fixes: 715c5ce454a6 ("libbpf: Add low level TC-BPF management API")
Cc: Kumar Kartikeya Dwivedi <memxor@xxxxxxxxx>
Signed-off-by: Yonghong Song <yhs@xxxxxx>
---
tools/lib/bpf/netlink.c | 20 ++++++++++++++++++++
1 file changed, 20 insertions(+)
Changelog:
v1 -> v2:
- gcc 8.3 doesn't like macro condition
(__TCA_BPF_MAX - 1) <= 10
where __TCA_BPF_MAX is an enumerator value.
So define TCA_BPF_ID macro without macro condition.
diff --git a/tools/lib/bpf/netlink.c b/tools/lib/bpf/netlink.c
index 39f25e09b51e..e00660e0b87a 100644
--- a/tools/lib/bpf/netlink.c
+++ b/tools/lib/bpf/netlink.c
@@ -22,6 +22,24 @@
#define SOL_NETLINK 270
#endif
+#ifndef TC_H_CLSACT
+#define TC_H_CLSACT TC_H_INGRESS
+#endif
+
+#ifndef TC_H_MIN_INGRESS
+#define TC_H_MIN_INGRESS 0xFFF2U
+#endif
+
+#ifndef TC_H_MIN_EGRESS
+#define TC_H_MIN_EGRESS 0xFFF3U
+#endif
+
+/* TCA_BPF_ID is an enumerate value in uapi/linux/pkt_cls.h.
+ * Declare it as a macro here so old system can still work
+ * without TCA_BPF_ID defined in pkt_cls.h.
+ */
+#define TCA_BPF_ID 11
+
typedef int (*libbpf_dump_nlmsg_t)(void *cookie, void *msg, struct nlattr **tb);
typedef int (*__dump_nlmsg_t)(struct nlmsghdr *nlmsg, libbpf_dump_nlmsg_t,
@@ -504,6 +522,8 @@ static int __get_tc_info(void *cookie, struct tcmsg *tc, struct nlattr **tb,
return -EINVAL;
if (!tb[TCA_OPTIONS])
return NL_CONT;
+ if (TCA_BPF_MAX < TCA_BPF_ID)
+ return -EOPNOTSUPP;
I'm a bit confused here. Generally what I want to have happen is compilation
to work always and then runtime to detect the errors. So when I compile my
libs on machine A and run it on machine B it does what I expect. This seems
like a bit of an ugly workaround to me. I would expect the user should
update the uapi?
The reason is due to the declaration
struct nlattr *tbb[TCA_BPF_MAX + 1];
so I have to have the above to check to ensure we
don't have out-of-bound access.
Alternative, I can redefine macro TCA_BPF_MAX to be the value
based on the *current* repo, we should be fine, I think.
I'm confused why upstream libbpf compilation is failing for you. There is already a
copy of pkt_sched.h with all the defines you need under:
tools/include/uapi/linux/pkt_sched.h
Are you saying this is not being included from tools/lib/bpf/ ? Afaik, it should be
(so the patch should not be needed).
Thanks,
Daniel
