[PATCH net-next v17 03/15] tls: reject rekey attempts on an existing HW-offloaded connection

[Rishikesh Jethwani <rjethwani@purestorage.com>]

On a TLS 1.3 rekey, do_tls_setsockopt_conf() must not set up a brand-new
device offload: reject the rekey with -EOPNOTSUPP for a HW-offloaded
connection (HW KeyUpdate is not supported yet, and we must not fall back
to software mid-connection), and for a SW-offloaded one re-init the
software crypto state via tls_set_sw_offload() directly.

Do this by moving the reject into the device-offload helpers and shaping
the dispatch in its final form:

  - tls_set_device_offload() and tls_set_device_offload_rx() reject any
    non-initial call (tx_conf / rx_conf != TLS_BASE) with -EOPNOTSUPP.

  - do_tls_setsockopt_conf() always calls the device helper and, on
    failure, either propagates the error (rekey on a HW connection) or
    falls back to tls_set_sw_offload() (initial install, or rekey on a
    SW connection).

Prep for the following patches: "tls: add TLS 1.3 hardware offload
support" drops the TLS_1_2_VERSION guards in those helpers (which today
also happen to reject a TLS 1.3 rekey), and the KeyUpdate patches replace
the reject guards above with real rekey handling in the helpers, leaving
the do_tls_setsockopt_conf() dispatch unchanged.

Signed-off-by: Rishikesh Jethwani <rjethwani@purestorage.com>
---
 net/tls/tls_device.c | 18 ++++++++++++++++++
 net/tls/tls_main.c   | 22 ++++++++++++++++++----
 2 files changed, 36 insertions(+), 4 deletions(-)

diff --git a/net/tls/tls_device.c b/net/tls/tls_device.c
index f11d0528fc43..f5e1b6b61ce3 100644
--- a/net/tls/tls_device.c
+++ b/net/tls/tls_device.c
@@ -1077,6 +1077,15 @@ int tls_set_device_offload(struct sock *sk)
 	ctx = tls_get_ctx(sk);
 	prot = &ctx->prot_info;
 
+	/* A rekey (setsockopt on an already-configured socket) is not
+	 * supported on the device offload path yet; reject it here so the
+	 * caller can decide (propagate the error for a HW connection, or
+	 * re-init software crypto for a SW one). KeyUpdate support replaces
+	 * this guard with real rekey handling.
+	 */
+	if (ctx->tx_conf != TLS_BASE)
+		return -EOPNOTSUPP;
+
 	if (ctx->priv_ctx_tx)
 		return -EEXIST;
 
@@ -1202,6 +1211,15 @@ int tls_set_device_offload_rx(struct sock *sk, struct tls_context *ctx)
 	if (ctx->crypto_recv.info.version != TLS_1_2_VERSION)
 		return -EOPNOTSUPP;
 
+	/* A rekey (setsockopt on an already-configured socket) is not
+	 * supported on the device offload path yet; reject it here so the
+	 * caller can decide (propagate the error for a HW connection, or
+	 * re-init software crypto for a SW one). KeyUpdate support replaces
+	 * this guard with real rekey handling.
+	 */
+	if (ctx->rx_conf != TLS_BASE)
+		return -EOPNOTSUPP;
+
 	netdev = get_netdev_for_sock(sk);
 	if (!netdev) {
 		pr_err_ratelimited("%s: netdev not found\n", __func__);
diff --git a/net/tls/tls_main.c b/net/tls/tls_main.c
index fbb274287aa5..15e83e853f22 100644
--- a/net/tls/tls_main.c
+++ b/net/tls/tls_main.c
@@ -713,8 +713,15 @@ static int do_tls_setsockopt_conf(struct sock *sk, sockptr_t optval,
 		rc = tls_set_device_offload(sk);
 		conf = TLS_HW;
 		if (!rc) {
-			TLS_INC_STATS(sock_net(sk), LINUX_MIB_TLSTXDEVICE);
-			TLS_INC_STATS(sock_net(sk), LINUX_MIB_TLSCURRTXDEVICE);
+			if (!update) {
+				TLS_INC_STATS(sock_net(sk), LINUX_MIB_TLSTXDEVICE);
+				TLS_INC_STATS(sock_net(sk), LINUX_MIB_TLSCURRTXDEVICE);
+			}
+		} else if (update && ctx->tx_conf == TLS_HW) {
+			/* HW rekey failed - return the actual error.
+			 * Cannot fall back to SW for an existing HW connection.
+			 */
+			goto err_crypto_info;
 		} else {
 			rc = tls_set_sw_offload(sk, 1,
 						update ? crypto_info : NULL);
@@ -733,8 +740,15 @@ static int do_tls_setsockopt_conf(struct sock *sk, sockptr_t optval,
 		rc = tls_set_device_offload_rx(sk, ctx);
 		conf = TLS_HW;
 		if (!rc) {
-			TLS_INC_STATS(sock_net(sk), LINUX_MIB_TLSRXDEVICE);
-			TLS_INC_STATS(sock_net(sk), LINUX_MIB_TLSCURRRXDEVICE);
+			if (!update) {
+				TLS_INC_STATS(sock_net(sk), LINUX_MIB_TLSRXDEVICE);
+				TLS_INC_STATS(sock_net(sk), LINUX_MIB_TLSCURRRXDEVICE);
+			}
+		} else if (update && ctx->rx_conf == TLS_HW) {
+			/* HW rekey failed - return the actual error.
+			 * Cannot fall back to SW for an existing HW connection.
+			 */
+			goto err_crypto_info;
 		} else {
 			rc = tls_set_sw_offload(sk, 0,
 						update ? crypto_info : NULL);
-- 
2.50.1