[PATCH bpf-next v3 09/14] selftests/bpf: move ip checksum helper to network helpers

[eBPF Foundation]

xdp_metadata test has a small helper computing ipv4 checksums to allow
manually building packets.

Move this helper to network_helpers to share it with other tests.

Signed-off-by: Alexis Lothoré (eBPF Foundation) <alexis.loth...@bootlin.com>
---
Changes in v3:
- use csum_partial for intermediate helper name to keep sync with the
  corresponding kernel helper
- provide byte count instead of half-word count to csum_partial

Changes in v2:
- new patch
---
 tools/testing/selftests/bpf/network_helpers.h      | 24 ++++++++++++++++++++++
 .../selftests/bpf/prog_tests/xdp_metadata.c        | 19 +----------------
 2 files changed, 25 insertions(+), 18 deletions(-)

diff --git a/tools/testing/selftests/bpf/network_helpers.h 
b/tools/testing/selftests/bpf/network_helpers.h
index 
c72c16e1aff825439896b38e59962ffafe92dc71..5ef909f766eb9ac2dd5be67b99245b4676ce4f5f
 100644
--- a/tools/testing/selftests/bpf/network_helpers.h
+++ b/tools/testing/selftests/bpf/network_helpers.h
@@ -104,6 +104,30 @@ static __u16 csum_fold(__u32 csum)
        return (__u16)~csum;
 }
 
+static __wsum csum_partial(const void *buf, int len, __wsum sum)
+{
+       __u16 *p = (__u16 *)buf;
+       int num_u16 = len >> 1;
+       int i;
+
+       for (i = 0; i < num_u16; i++)
+               sum += p[i];
+
+       return sum;
+}
+
+static inline __sum16 build_ip_csum(struct iphdr *iph)
+{
+       __u32 sum = 0;
+       __u16 *p;
+
+       iph->check = 0;
+       p = (void *)iph;
+       sum = csum_partial(p, iph->ihl << 2, 0);
+
+       return csum_fold(sum);
+}
+
 static inline __sum16 csum_tcpudp_magic(__be32 saddr, __be32 daddr,
                                        __u32 len, __u8 proto,
                                        __wsum csum)
diff --git a/tools/testing/selftests/bpf/prog_tests/xdp_metadata.c 
b/tools/testing/selftests/bpf/prog_tests/xdp_metadata.c
index 
c87ee2bf558c1a7fb726cae0aa7b3d3735fb1aac..7f8e161655336127e5bd7a573d1a09db85a92f53
 100644
--- a/tools/testing/selftests/bpf/prog_tests/xdp_metadata.c
+++ b/tools/testing/selftests/bpf/prog_tests/xdp_metadata.c
@@ -133,23 +133,6 @@ static void close_xsk(struct xsk *xsk)
        munmap(xsk->umem_area, UMEM_SIZE);
 }
 
-static void ip_csum(struct iphdr *iph)
-{
-       __u32 sum = 0;
-       __u16 *p;
-       int i;
-
-       iph->check = 0;
-       p = (void *)iph;
-       for (i = 0; i < sizeof(*iph) / sizeof(*p); i++)
-               sum += p[i];
-
-       while (sum >> 16)
-               sum = (sum & 0xffff) + (sum >> 16);
-
-       iph->check = ~sum;
-}
-
 static int generate_packet(struct xsk *xsk, __u16 dst_port)
 {
        struct xsk_tx_metadata *meta;
@@ -192,7 +175,7 @@ static int generate_packet(struct xsk *xsk, __u16 dst_port)
        iph->protocol = IPPROTO_UDP;
        ASSERT_EQ(inet_pton(FAMILY, TX_ADDR, &iph->saddr), 1, 
"inet_pton(TX_ADDR)");
        ASSERT_EQ(inet_pton(FAMILY, RX_ADDR, &iph->daddr), 1, 
"inet_pton(RX_ADDR)");
-       ip_csum(iph);
+       iph->check = build_ip_csum(iph);
 
        udph->source = htons(UDP_SOURCE_PORT);
        udph->dest = htons(dst_port);

-- 
2.47.0