[PATCH net-next 12/23] rxrpc: Allow for a security trailer in a packet

[David Howells]

Allow for a security trailer to added to a packet.  The size is stored in
conn->security_trailer.  Note any size alignment set by the security class
must be applied after subtracting the trailer (but the alignment includes
the security header, which is assumed to be encrypted).

Signed-off-by: David Howells <dhowe...@redhat.com>
---

 net/rxrpc/ar-internal.h |    1 +
 net/rxrpc/sendmsg.c     |   28 ++++++++++++++++------------
 2 files changed, 17 insertions(+), 12 deletions(-)

diff --git a/net/rxrpc/ar-internal.h b/net/rxrpc/ar-internal.h
index dce48162f6c2..5aacd6d7cf28 100644
--- a/net/rxrpc/ar-internal.h
+++ b/net/rxrpc/ar-internal.h
@@ -455,6 +455,7 @@ struct rxrpc_connection {
        u32                     service_id;     /* Service ID, possibly 
upgraded */
        u8                      size_align;     /* data size alignment (for 
security) */
        u8                      security_size;  /* security header size */
+       u8                      security_trailer; /* Security trailer size */
        u8                      security_ix;    /* security type */
        u8                      out_clientflag; /* RXRPC_CLIENT_INITIATED if we 
are client */
        u8                      bundle_shift;   /* Index into 
bundle->avail_chans */
diff --git a/net/rxrpc/sendmsg.c b/net/rxrpc/sendmsg.c
index d27140c836cc..258224bb1227 100644
--- a/net/rxrpc/sendmsg.c
+++ b/net/rxrpc/sendmsg.c
@@ -327,7 +327,7 @@ static int rxrpc_send_data(struct rxrpc_sock *rx,
                        rxrpc_send_ack_packet(call, false, NULL);
 
                if (!skb) {
-                       size_t size, chunk, max, space;
+                       size_t size, chunk, limit, space, shdr;
 
                        _debug("alloc");
 
@@ -342,18 +342,22 @@ static int rxrpc_send_data(struct rxrpc_sock *rx,
                                        goto maybe_error;
                        }
 
-                       max = RXRPC_JUMBO_DATALEN;
-                       max -= call->conn->security_size;
-                       max &= ~(call->conn->size_align - 1UL);
-
-                       chunk = max;
-                       if (chunk > msg_data_left(msg) && !more)
+                       /* Work out the maximum size of a packet.  Assume that
+                        * the security header is going to be in the padded
+                        * region (enc blocksize), but the trailer is not.
+                        */
+                       shdr = call->conn->security_size;
+                       limit = RXRPC_JUMBO_DATALEN;
+                       limit -= call->conn->security_trailer;
+                       space = round_down(limit, call->conn->size_align);
+
+                       chunk = space - shdr;
+                       if (msg_data_left(msg) < chunk && !more) {
                                chunk = msg_data_left(msg);
+                               space = round_up(shdr + chunk, 
call->conn->size_align);
+                       }
 
-                       space = chunk + call->conn->size_align;
-                       space &= ~(call->conn->size_align - 1UL);
-
-                       size = space + call->conn->security_size;
+                       size = space + call->conn->security_trailer;
 
                        _debug("SIZE: %zu/%zu/%zu", chunk, space, size);
 
@@ -425,7 +429,7 @@ static int rxrpc_send_data(struct rxrpc_sock *rx,
                        size_t pad;
 
                        /* pad out if we're using security */
-                       if (conn->security_ix) {
+                       if (conn->size_align > 0) {
                                pad = conn->security_size + skb->mark;
                                pad = conn->size_align - pad;
                                pad &= conn->size_align - 1;