selftests/bpf: remove xdp_synproxy IP_DF check

In real world production websites, the IP_DF flag
is not always set for each packet from these websites.
the IP_DF flag check breaks Internet connection to
these websites for home based firewall like BPFire
when XDP synproxy program is attached to firewall
Internet facing side interface. see [0]

[0] https://github.com/vincentmli/BPFire/issues/59

Signed-off-by: Vincent Li <vincent.mc.li@gmail.com>
Link: https://lore.kernel.org/r/20241025031952.1351150-1-vincent.mc.li@gmail.com
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>

diff --git a/tools/testing/selftests/bpf/progs/xdp_synproxy_kern.c b/tools/testing/selftests/bpf/progs/xdp_synproxy_kern.c
index f8f5dc9f72b8ca7168605d5f8ab3fc245843ffc2..62b8e29ced9fb9c157ab8779fc7a8fae2156412b 100644 (file)
--- a/tools/testing/selftests/bpf/progs/xdp_synproxy_kern.c
+++ b/tools/testing/selftests/bpf/progs/xdp_synproxy_kern.c
@@ -21,7 +21,6 @@
 
 #define tcp_flag_word(tp) (((union tcp_word_hdr *)(tp))->words[3])
 
-#define IP_DF 0x4000
 #define IP_MF 0x2000
 #define IP_OFFSET 0x1fff
 
@@ -442,7 +441,7 @@ static __always_inline int tcp_lookup(void *ctx, struct header_pointers *hdr, bo
                /* TCP doesn't normally use fragments, and XDP can't reassemble
                 * them.
                 */
-               if ((hdr->ipv4->frag_off & bpf_htons(IP_DF | IP_MF | IP_OFFSET)) != bpf_htons(IP_DF))
+               if ((hdr->ipv4->frag_off & bpf_htons(IP_MF | IP_OFFSET)) != 0)
                        return XDP_DROP;
 
                tup.ipv4.saddr = hdr->ipv4->saddr;