mptcp: send out checksum for MP_CAPABLE with data

If the checksum is enabled, send out the data checksum with the
MP_CAPABLE suboption with data.

In mptcp_established_options_mp, save the data checksum in
opts->ext_copy.csum. In mptcp_write_options, adjust the option length and
send it out with the MP_CAPABLE suboption.

Co-developed-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Geliang Tang <geliangtang@gmail.com>
Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/mptcp/options.c b/net/mptcp/options.c
index bb3a1f3..b4da08d 100644 (file)
--- a/net/mptcp/options.c
+++ b/net/mptcp/options.c
@@ -439,6 +439,7 @@ static bool mptcp_established_options_mp(struct sock *sk, struct sk_buff *skb,
        struct mptcp_sock *msk = mptcp_sk(subflow->conn);
        struct mptcp_ext *mpext;
        unsigned int data_len;
+       u8 len;
 
        /* When skb is not available, we better over-estimate the emitted
         * options len. A full DSS option (28 bytes) is longer than
@@ -474,10 +475,16 @@ static bool mptcp_established_options_mp(struct sock *sk, struct sk_buff *skb,
                 * packets that start the first subflow of an MPTCP connection,
                 * as well as the first packet that carries data
                 */
-               if (data_len > 0)
-                       *size = ALIGN(TCPOLEN_MPTCP_MPC_ACK_DATA, 4);
-               else
+               if (data_len > 0) {
+                       len = TCPOLEN_MPTCP_MPC_ACK_DATA;
+                       if (opts->csum_reqd) {
+                               opts->ext_copy.csum = mpext->csum;
+                               len += TCPOLEN_MPTCP_DSS_CHECKSUM;
+                       }
+                       *size = ALIGN(len, 4);
+               } else {
                        *size = TCPOLEN_MPTCP_MPC_ACK;
+               }
 
                pr_debug("subflow=%p, local_key=%llu, remote_key=%llu map_len=%d",
                         subflow, subflow->local_key, subflow->remote_key,
@@ -1122,6 +1129,25 @@ static void mptcp_set_rwin(const struct tcp_sock *tp)
                WRITE_ONCE(msk->rcv_wnd_sent, ack_seq);
 }
 
+static u16 mptcp_make_csum(const struct mptcp_ext *mpext)
+{
+       struct csum_pseudo_header header;
+       __wsum csum;
+
+       /* cfr RFC 8684 3.3.1.:
+        * the data sequence number used in the pseudo-header is
+        * always the 64-bit value, irrespective of what length is used in the
+        * DSS option itself.
+        */
+       header.data_seq = cpu_to_be64(mpext->data_seq);
+       header.subflow_seq = htonl(mpext->subflow_seq);
+       header.data_len = htons(mpext->data_len);
+       header.csum = 0;
+
+       csum = csum_partial(&header, sizeof(header), ~csum_unfold(mpext->csum));
+       return (__force u16)csum_fold(csum);
+}
+
 void mptcp_write_options(__be32 *ptr, const struct tcp_sock *tp,
                         struct mptcp_out_options *opts)
 {
@@ -1129,14 +1155,17 @@ void mptcp_write_options(__be32 *ptr, const struct tcp_sock *tp,
             OPTION_MPTCP_MPC_ACK) & opts->suboptions) {
                u8 len, flag = MPTCP_CAP_HMAC_SHA256;
 
-               if (OPTION_MPTCP_MPC_SYN & opts->suboptions)
+               if (OPTION_MPTCP_MPC_SYN & opts->suboptions) {
                        len = TCPOLEN_MPTCP_MPC_SYN;
-               else if (OPTION_MPTCP_MPC_SYNACK & opts->suboptions)
+               } else if (OPTION_MPTCP_MPC_SYNACK & opts->suboptions) {
                        len = TCPOLEN_MPTCP_MPC_SYNACK;
-               else if (opts->ext_copy.data_len)
+               } else if (opts->ext_copy.data_len) {
                        len = TCPOLEN_MPTCP_MPC_ACK_DATA;
-               else
+                       if (opts->csum_reqd)
+                               len += TCPOLEN_MPTCP_DSS_CHECKSUM;
+               } else {
                        len = TCPOLEN_MPTCP_MPC_ACK;
+               }
 
                if (opts->csum_reqd)
                        flag |= MPTCP_CAP_CHECKSUM_REQD;
@@ -1159,8 +1188,13 @@ void mptcp_write_options(__be32 *ptr, const struct tcp_sock *tp,
                if (!opts->ext_copy.data_len)
                        goto mp_capable_done;
 
-               put_unaligned_be32(opts->ext_copy.data_len << 16 |
-                                  TCPOPT_NOP << 8 | TCPOPT_NOP, ptr);
+               if (opts->csum_reqd) {
+                       put_unaligned_be32(opts->ext_copy.data_len << 16 |
+                                          mptcp_make_csum(&opts->ext_copy), ptr);
+               } else {
+                       put_unaligned_be32(opts->ext_copy.data_len << 16 |
+                                          TCPOPT_NOP << 8 | TCPOPT_NOP, ptr);
+               }
                ptr += 1;
        }