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>> ^ >> .../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 >> Signed-off-by: Yonghong Song >> --- >> 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. > > Or should we (maybe just libbpf git repo?) include the defines needed? The > change here seems likely to cause issues where someone compiles on old > kernel then tries to run it later on newer kernel and is confused when they > get EOPNOTSUPP. That is true. Compiling in old system and then using in new system might have issues. > > Did I miss something? What if we just include the enum directly and > wrap in ifndef? This is how I've dealt with these dependencies on > other libs/apps. As I am mentioned in the commit message, we cannot use a simple ifndef to control including the enum since header file in the old system contains *some* enumerators. Testing whether a particular enumerator should be included requires some arithmetic (minus) in the macro condition and some compiler (e.g., gcc 8.3) does not like it. But I think by defining TCA_BPF_MAX explicitly should solve the problem. Will send a new patch soon. > >> >> libbpf_nla_parse_nested(tbb, TCA_BPF_MAX, tb[TCA_OPTIONS], NULL); >> if (!tbb[TCA_BPF_ID]) >> -- >> 2.30.2