On Mon, Feb 12, 2024 at 09:18:14AM -0800, Guenter Roeck wrote:
Almost. Turns out the csum parameter of csum_ipv6_magic() needs to be in
network byte order, and the length parameter needs to be in host byte order.
So instead of
data.len = data_ptr->len;
data.csum = (__force __wsum)htonl((__force u32)data_ptr->csum);
it needs to be something like
data.len = ntohl(data_ptr->len);
data.csum = data_ptr->csum;
Also, as you mentioned, either the returned checksum or the expected
checksum needs to be converted for the comparison because one is in
network byte order and the other in host byte order.
for (int i = 0; i < NUM_IPv6_TESTS; i++) {
struct args {
struct in6_addr saddr;
struct in6_addr daddr;
__be32 len;
__wsum csum;
unsigned char proto;
} __packed data = (struct args *)(random_buf + i);
CHECK_EQ(cpu_to_le16(expected_csum_ipv6_magic[i]),
csum_ipv6_magic(data.saddr, data.daddr, ntohl(data.len),
data.proto, data.sum));
}
and to hell with field-by-field copying. __packed here will tell the compiler
that alignment of the entire thing is 1 - the total size of fields is 41 bytes,
so "no padding" translates into "can't even assume that address is even".