1 files changed, 70 insertions, 0 deletions

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index ab66683b8043..6efbae0e5512 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -2459,6 +2459,76 @@ static unsigned long tcp_md5sig_users;
 static struct tcp_md5sig_pool **tcp_md5sig_pool;
 static DEFINE_SPINLOCK(tcp_md5sig_pool_lock);
 
+int tcp_calc_md5_hash(char *md5_hash, struct tcp_md5sig_key *key,
+                      int bplen,
+                      struct tcphdr *th, unsigned int tcplen,
+                      struct tcp_md5sig_pool *hp)
+{
+        struct scatterlist sg[4];
+        __u16 data_len;
+        int block = 0;
+        __sum16 cksum;
+        struct hash_desc *desc = &hp->md5_desc;
+        int err;
+        unsigned int nbytes = 0;
+
+        sg_init_table(sg, 4);
+
+        /* 1. The TCP pseudo-header */
+        sg_set_buf(&sg[block++], &hp->md5_blk, bplen);
+        nbytes += bplen;
+
+        /* 2. The TCP header, excluding options, and assuming a
+         * checksum of zero
+         */
+        cksum = th->check;
+        th->check = 0;
+        sg_set_buf(&sg[block++], th, sizeof(*th));
+        nbytes += sizeof(*th);
+
+        /* 3. The TCP segment data (if any) */
+        data_len = tcplen - (th->doff << 2);
+        if (data_len > 0) {
+                u8 *data = (u8 *)th + (th->doff << 2);
+                sg_set_buf(&sg[block++], data, data_len);
+                nbytes += data_len;
+        }
+
+        /* 4. an independently-specified key or password, known to both
+         * TCPs and presumably connection-specific
+         */
+        sg_set_buf(&sg[block++], key->key, key->keylen);
+        nbytes += key->keylen;
+
+        sg_mark_end(&sg[block - 1]);
+
+        /* Now store the hash into the packet */
+        err = crypto_hash_init(desc);
+        if (err) {
+                if (net_ratelimit())
+                        printk(KERN_WARNING "%s(): hash_init failed\n", __func__);
+                return -1;
+        }
+        err = crypto_hash_update(desc, sg, nbytes);
+        if (err) {
+                if (net_ratelimit())
+                        printk(KERN_WARNING "%s(): hash_update failed\n", __func__);
+                return -1;
+        }
+        err = crypto_hash_final(desc, md5_hash);
+        if (err) {
+                if (net_ratelimit())
+                        printk(KERN_WARNING "%s(): hash_final failed\n", __func__);
+                return -1;
+        }
+
+        /* Reset header */
+        th->check = cksum;
+
+        return 0;
+}
+EXPORT_SYMBOL(tcp_calc_md5_hash);
+
 static void __tcp_free_md5sig_pool(struct tcp_md5sig_pool **pool)
 {
         int cpu;