SHA_DIGEST_WORDS  438 include/net/tcp.h extern __u32 syncookie_secret[2][16-4+SHA_DIGEST_WORDS];
SHA_DIGEST_WORDS   27 net/ipv4/syncookies.c __u32 syncookie_secret[2][16-4+SHA_DIGEST_WORDS];
SHA_DIGEST_WORDS   25 net/ipv6/syncookies.c extern __u32 syncookie_secret[2][16-4+SHA_DIGEST_WORDS];