[PATCH bpf-next v2 11/13] selftests/bpf: add network helpers to generate udp checksums

["Alexis Lothoré (eBPF Foundation)" <alexis.lothore@bootlin.com>]

network_helpers.c provides some helpers to generate ip checksums or ip
pseudo-header checksums, but not for upper layers (eg: udp checksums)

Add helpers for udp checksum to allow manually building udp packets.

Signed-off-by: Alexis Lothoré (eBPF Foundation) <alexis.lothore@bootlin.com>
---
Changes in v2:
- new patch
---
 tools/testing/selftests/bpf/network_helpers.h | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

diff --git a/tools/testing/selftests/bpf/network_helpers.h b/tools/testing/selftests/bpf/network_helpers.h
index 6d1ae56080c56a65c437899c32566f0e4c496c33..fa82269f7a169a518ba210fa8641eba02f262333 100644
--- a/tools/testing/selftests/bpf/network_helpers.h
+++ b/tools/testing/selftests/bpf/network_helpers.h
@@ -161,6 +161,33 @@ build_ipv6_pseudo_header_csum(const struct in6_addr *saddr,
 	return csum_fold((__u32)s);
 }
 
+static inline __sum16 build_udp_v4_csum(const struct iphdr *iph, __u8 l4_proto,
+					__u16 l4_len, const void *l4_start,
+					int num_words)
+{
+	unsigned long pseudo_sum;
+	int num_u16 = sizeof(iph->saddr); /* halfwords: twice byte len */
+
+	pseudo_sum = add_csum_hword((void *)&iph->saddr, num_u16);
+	pseudo_sum += htons(l4_proto);
+	pseudo_sum += l4_len;
+	pseudo_sum += add_csum_hword(l4_start, num_words);
+	return csum_fold(pseudo_sum);
+}
+
+static inline __sum16 build_udp_v6_csum(const struct ipv6hdr *ip6h,
+					const void *l4_start, int num_words)
+{
+	unsigned long pseudo_sum;
+	int num_u16 = sizeof(ip6h->saddr); /* halfwords: twice byte len */
+
+	pseudo_sum = add_csum_hword((void *)&ip6h->saddr, num_u16);
+	pseudo_sum += htons(ip6h->nexthdr);
+	pseudo_sum += ip6h->payload_len;
+	pseudo_sum += add_csum_hword(l4_start, num_words);
+	return csum_fold(pseudo_sum);
+}
+
 struct tmonitor_ctx;
 
 #ifdef TRAFFIC_MONITOR

-- 
2.47.0