On Sat, Feb 26, 2022 at 06:44 PM -08, Alexei Starovoitov wrote:
> On Tue, Feb 22, 2022 at 07:25:58PM +0100, Ilya Leoshkevich wrote:
>> On big-endian, the port is available in the second __u16, not the first
>> one. Therefore, provide a big-endian-specific definition that reflects
>> that. Also, define remote_port_compat in order to have nicer
>> architecture-agnostic code in the verifier and in tests.
>>
>> Fixes: 9a69e2b385f4 ("bpf: Make remote_port field in struct bpf_sk_lookup 16-bit wide")
>> Signed-off-by: Ilya Leoshkevich <iii@xxxxxxxxxxxxx>
>> ---
>> include/uapi/linux/bpf.h | 17 +++++++++++++++--
>> net/core/filter.c | 5 ++---
>> tools/include/uapi/linux/bpf.h | 17 +++++++++++++++--
>> 3 files changed, 32 insertions(+), 7 deletions(-)
>>
>> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
>> index afe3d0d7f5f2..7b0e5efa58e0 100644
>> --- a/include/uapi/linux/bpf.h
>> +++ b/include/uapi/linux/bpf.h
>> @@ -10,6 +10,7 @@
>>
>> #include <linux/types.h>
>> #include <linux/bpf_common.h>
>> +#include <asm/byteorder.h>
>>
>> /* Extended instruction set based on top of classic BPF */
>>
>> @@ -6453,8 +6454,20 @@ struct bpf_sk_lookup {
>> __u32 protocol; /* IP protocol (IPPROTO_TCP, IPPROTO_UDP) */
>> __u32 remote_ip4; /* Network byte order */
>> __u32 remote_ip6[4]; /* Network byte order */
>> - __be16 remote_port; /* Network byte order */
>> - __u16 :16; /* Zero padding */
>> + union {
>> + struct {
>> +#if defined(__BYTE_ORDER) ? __BYTE_ORDER == __LITTLE_ENDIAN : defined(__LITTLE_ENDIAN)
>> + __be16 remote_port; /* Network byte order */
>> + __u16 :16; /* Zero padding */
>> +#elif defined(__BYTE_ORDER) ? __BYTE_ORDER == __BIG_ENDIAN : defined(__BIG_ENDIAN)
>> + __u16 :16; /* Zero padding */
>> + __be16 remote_port; /* Network byte order */
>> +#else
>> +#error unspecified endianness
>> +#endif
>> + };
>> + __u32 remote_port_compat;
>
> Sorry this hack is not an option.
> Don't have any suggestions at this point. Pls come up with something else.
I think we can keep the bpf_sk_lookup definition as is, if we leave the
4-byte load from remote_port offset quirky behavior on little-endian.
Please take a look at the test fix I've posted for 4-byte load from
bpf_sock dst_port that works for me on x86_64 and s390. It is exactly
the same case as we're dealing with here:
https://lore.kernel.org/bpf/20220227202757.519015-4-jakub@xxxxxxxxxxxxxx/T/#u
