tcp: md5: add TCP_MD5SIG_EXT socket option to set a key address prefix

Replace first padding in the tcp_md5sig structure with a new flag field
and address prefix length so it can be specified when configuring a new
key for TCP MD5 signature. The tcpm_flags field will only be used if the
socket option is TCP_MD5SIG_EXT to avoid breaking existing programs, and
tcpm_prefixlen only when the TCP_MD5SIG_FLAG_PREFIX flag is set.

Signed-off-by: Bob Gilligan <gilligan@arista.com>
Signed-off-by: Eric Mowat <mowat@arista.com>
Signed-off-by: Ivan Delalande <colona@arista.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 12 insertions, 4 deletions

diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index a3c67866b780..bf407f3e20dd 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -1066,11 +1066,12 @@ static void tcp_clear_md5_list(struct sock *sk)
         }
 }
 
-static int tcp_v4_parse_md5_keys(struct sock *sk, char __user *optval,
-                                 int optlen)
+static int tcp_v4_parse_md5_keys(struct sock *sk, int optname,
+                                 char __user *optval, int optlen)
 {
         struct tcp_md5sig cmd;
         struct sockaddr_in *sin = (struct sockaddr_in *)&cmd.tcpm_addr;
+        u8 prefixlen = 32;
 
         if (optlen < sizeof(cmd))
                 return -EINVAL;
@@ -1081,15 +1082,22 @@ static int tcp_v4_parse_md5_keys(struct sock *sk, char __user *optval,
         if (sin->sin_family != AF_INET)
                 return -EINVAL;
 
+        if (optname == TCP_MD5SIG_EXT &&
+            cmd.tcpm_flags & TCP_MD5SIG_FLAG_PREFIX) {
+                prefixlen = cmd.tcpm_prefixlen;
+                if (prefixlen > 32)
+                        return -EINVAL;
+        }
+
         if (!cmd.tcpm_keylen)
                 return tcp_md5_do_del(sk, (union tcp_md5_addr *)&sin->sin_addr.s_addr,
-                                      AF_INET, 32);
+                                      AF_INET, prefixlen);
 
         if (cmd.tcpm_keylen > TCP_MD5SIG_MAXKEYLEN)
                 return -EINVAL;
 
         return tcp_md5_do_add(sk, (union tcp_md5_addr *)&sin->sin_addr.s_addr,
-                              AF_INET, 32, cmd.tcpm_key, cmd.tcpm_keylen,
+                              AF_INET, prefixlen, cmd.tcpm_key, cmd.tcpm_keylen,
                               GFP_KERNEL);
 }