xdp_metadata test has a small helper computing ipv 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.lothore@bootlin.com>
---
Changes in v2:
- new patch
---
 tools/testing/selftests/bpf/network_helpers.h      | 23 ++++++++++++++++++++++
 .../selftests/bpf/prog_tests/xdp_metadata.c        | 19 +-----------------
 2 files changed, 24 insertions(+), 18 deletions(-)

diff --git a/tools/testing/selftests/bpf/network_helpers.h b/tools/testing/selftests/bpf/network_helpers.h
index c72c16e1aff825439896b38e59962ffafe92dc71..c9b72960c651ab9fb249f6eb9e153b8416b7a488 100644
--- a/tools/testing/selftests/bpf/network_helpers.h
+++ b/tools/testing/selftests/bpf/network_helpers.h
@@ -104,6 +104,29 @@ static __u16 csum_fold(__u32 csum)
 	return (__u16)~csum;
 }
 
+static unsigned long add_csum_hword(const __u16 *start, int num_u16)
+{
+	unsigned long sum = 0;
+	int i;
+
+	for (i = 0; i < num_u16; i++)
+		sum += start[i];
+
+	return sum;
+}
+
+static inline __sum16 build_ip_csum(struct iphdr *iph)
+{
+	__u32 sum = 0;
+	__u16 *p;
+
+	iph->check = 0;
+	p = (void *)iph;
+	sum = add_csum_hword(p, iph->ihl << 1);
+
+	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

On 11/14, Alexis Lothoré (eBPF Foundation) wrote:
> xdp_metadata test has a small helper computing ipv 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.lothore@bootlin.com>
> ---
> Changes in v2:
> - new patch
> ---
>  tools/testing/selftests/bpf/network_helpers.h      | 23 ++++++++++++++++++++++
>  .../selftests/bpf/prog_tests/xdp_metadata.c        | 19 +-----------------
>  2 files changed, 24 insertions(+), 18 deletions(-)
> 
> diff --git a/tools/testing/selftests/bpf/network_helpers.h b/tools/testing/selftests/bpf/network_helpers.h
> index c72c16e1aff825439896b38e59962ffafe92dc71..c9b72960c651ab9fb249f6eb9e153b8416b7a488 100644
> --- a/tools/testing/selftests/bpf/network_helpers.h
> +++ b/tools/testing/selftests/bpf/network_helpers.h
> @@ -104,6 +104,29 @@ static __u16 csum_fold(__u32 csum)
>  	return (__u16)~csum;
>  }
>  

[..]

> +static unsigned long add_csum_hword(const __u16 *start, int num_u16)
> +{
> +	unsigned long sum = 0;
> +	int i;
> +
> +	for (i = 0; i < num_u16; i++)
> +		sum += start[i];
> +
> +	return sum;
> +}

Sorry for nitpicking, but can we call it csum_partial? And match
kernel's prototype with extra sum argument? Should be more greppable
for the future test cases that might want to use it...

Hello Stanislas,

On 11/15/24 16:32, Stanislav Fomichev wrote:
> On 11/14, Alexis Lothoré (eBPF Foundation) wrote:
>> +static unsigned long add_csum_hword(const __u16 *start, int num_u16)
>> +{
>> +	unsigned long sum = 0;
>> +	int i;
>> +
>> +	for (i = 0; i < num_u16; i++)
>> +		sum += start[i];
>> +
>> +	return sum;
>> +}
> 
> Sorry for nitpicking, but can we call it csum_partial? And match
> kernel's prototype with extra sum argument? Should be more greppable
> for the future test cases that might want to use it...

Sure. TBH I did not realize that those were based on the kernel ones. I'll
update this to keep the same prototype.


-- 
Alexis Lothoré, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com