tls: Add rx inline crypto offload

This patch completes the generic infrastructure to offload TLS crypto to a
network device. It enables the kernel to skip decryption and
authentication of some skbs marked as decrypted by the NIC. In the fast
path, all packets received are decrypted by the NIC and the performance
is comparable to plain TCP.

This infrastructure doesn't require a TCP offload engine. Instead, the
NIC only decrypts packets that contain the expected TCP sequence number.
Out-Of-Order TCP packets are provided unmodified. As a result, at the
worst case a received TLS record consists of both plaintext and ciphertext
packets. These partially decrypted records must be reencrypted,
only to be decrypted.

The notable differences between SW KTLS Rx and this offload are as
follows:
1. Partial decryption - Software must handle the case of a TLS record
that was only partially decrypted by HW. This can happen due to packet
reordering.
2. Resynchronization - tls_read_size calls the device driver to
resynchronize HW after HW lost track of TLS record framing in
the TCP stream.

Signed-off-by: Boris Pismenny <borisp@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 256 insertions, 22 deletions

diff --git a/net/tls/tls_device.c b/net/tls/tls_device.c
index 332a5d1459b6..4995d84d228d 100644
--- a/net/tls/tls_device.c
+++ b/net/tls/tls_device.c
@@ -52,7 +52,11 @@ static DEFINE_SPINLOCK(tls_device_lock);
 
 static void tls_device_free_ctx(struct tls_context *ctx)
 {
-        kfree(tls_offload_ctx_tx(ctx));
+        if (ctx->tx_conf == TLS_HW)
+                kfree(tls_offload_ctx_tx(ctx));
+
+        if (ctx->rx_conf == TLS_HW)
+                kfree(tls_offload_ctx_rx(ctx));
 
         kfree(ctx);
 }
@@ -70,10 +74,11 @@ static void tls_device_gc_task(struct work_struct *work)
         list_for_each_entry_safe(ctx, tmp, &gc_list, list) {
                 struct net_device *netdev = ctx->netdev;
 
-                if (netdev) {
+                if (netdev && ctx->tx_conf == TLS_HW) {
                         netdev->tlsdev_ops->tls_dev_del(netdev, ctx,
                                                         TLS_OFFLOAD_CTX_DIR_TX);
                         dev_put(netdev);
+                        ctx->netdev = NULL;
                 }
 
                 list_del(&ctx->list);
@@ -81,6 +86,22 @@ static void tls_device_gc_task(struct work_struct *work)
         }
 }
 
+static void tls_device_attach(struct tls_context *ctx, struct sock *sk,
+                              struct net_device *netdev)
+{
+        if (sk->sk_destruct != tls_device_sk_destruct) {
+                refcount_set(&ctx->refcount, 1);
+                dev_hold(netdev);
+                ctx->netdev = netdev;
+                spin_lock_irq(&tls_device_lock);
+                list_add_tail(&ctx->list, &tls_device_list);
+                spin_unlock_irq(&tls_device_lock);
+
+                ctx->sk_destruct = sk->sk_destruct;
+                sk->sk_destruct = tls_device_sk_destruct;
+        }
+}
+
 static void tls_device_queue_ctx_destruction(struct tls_context *ctx)
 {
         unsigned long flags;
@@ -180,13 +201,15 @@ void tls_device_sk_destruct(struct sock *sk)
         struct tls_context *tls_ctx = tls_get_ctx(sk);
         struct tls_offload_context_tx *ctx = tls_offload_ctx_tx(tls_ctx);
 
-        if (ctx->open_record)
-                destroy_record(ctx->open_record);
+        tls_ctx->sk_destruct(sk);
 
-        delete_all_records(ctx);
-        crypto_free_aead(ctx->aead_send);
-        ctx->sk_destruct(sk);
-        clean_acked_data_disable(inet_csk(sk));
+        if (tls_ctx->tx_conf == TLS_HW) {
+                if (ctx->open_record)
+                        destroy_record(ctx->open_record);
+                delete_all_records(ctx);
+                crypto_free_aead(ctx->aead_send);
+                clean_acked_data_disable(inet_csk(sk));
+        }
 
         if (refcount_dec_and_test(&tls_ctx->refcount))
                 tls_device_queue_ctx_destruction(tls_ctx);
@@ -519,6 +542,118 @@ static int tls_device_push_pending_record(struct sock *sk, int flags)
         return tls_push_data(sk, &msg_iter, 0, flags, TLS_RECORD_TYPE_DATA);
 }
 
+void handle_device_resync(struct sock *sk, u32 seq, u64 rcd_sn)
+{
+        struct tls_context *tls_ctx = tls_get_ctx(sk);
+        struct net_device *netdev = tls_ctx->netdev;
+        struct tls_offload_context_rx *rx_ctx;
+        u32 is_req_pending;
+        s64 resync_req;
+        u32 req_seq;
+
+        if (tls_ctx->rx_conf != TLS_HW)
+                return;
+
+        rx_ctx = tls_offload_ctx_rx(tls_ctx);
+        resync_req = atomic64_read(&rx_ctx->resync_req);
+        req_seq = ntohl(resync_req >> 32) - ((u32)TLS_HEADER_SIZE - 1);
+        is_req_pending = resync_req;
+
+        if (unlikely(is_req_pending) && req_seq == seq &&
+            atomic64_try_cmpxchg(&rx_ctx->resync_req, &resync_req, 0))
+                netdev->tlsdev_ops->tls_dev_resync_rx(netdev, sk,
+                                                      seq + TLS_HEADER_SIZE - 1,
+                                                      rcd_sn);
+}
+
+static int tls_device_reencrypt(struct sock *sk, struct sk_buff *skb)
+{
+        struct strp_msg *rxm = strp_msg(skb);
+        int err = 0, offset = rxm->offset, copy, nsg;
+        struct sk_buff *skb_iter, *unused;
+        struct scatterlist sg[1];
+        char *orig_buf, *buf;
+
+        orig_buf = kmalloc(rxm->full_len + TLS_HEADER_SIZE +
+                           TLS_CIPHER_AES_GCM_128_IV_SIZE, sk->sk_allocation);
+        if (!orig_buf)
+                return -ENOMEM;
+        buf = orig_buf;
+
+        nsg = skb_cow_data(skb, 0, &unused);
+        if (unlikely(nsg < 0)) {
+                err = nsg;
+                goto free_buf;
+        }
+
+        sg_init_table(sg, 1);
+        sg_set_buf(&sg[0], buf,
+                   rxm->full_len + TLS_HEADER_SIZE +
+                   TLS_CIPHER_AES_GCM_128_IV_SIZE);
+        skb_copy_bits(skb, offset, buf,
+                      TLS_HEADER_SIZE + TLS_CIPHER_AES_GCM_128_IV_SIZE);
+
+        /* We are interested only in the decrypted data not the auth */
+        err = decrypt_skb(sk, skb, sg);
+        if (err != -EBADMSG)
+                goto free_buf;
+        else
+                err = 0;
+
+        copy = min_t(int, skb_pagelen(skb) - offset,
+                     rxm->full_len - TLS_CIPHER_AES_GCM_128_TAG_SIZE);
+
+        if (skb->decrypted)
+                skb_store_bits(skb, offset, buf, copy);
+
+        offset += copy;
+        buf += copy;
+
+        skb_walk_frags(skb, skb_iter) {
+                copy = min_t(int, skb_iter->len,
+                             rxm->full_len - offset + rxm->offset -
+                             TLS_CIPHER_AES_GCM_128_TAG_SIZE);
+
+                if (skb_iter->decrypted)
+                        skb_store_bits(skb, offset, buf, copy);
+
+                offset += copy;
+                buf += copy;
+        }
+
+free_buf:
+        kfree(orig_buf);
+        return err;
+}
+
+int tls_device_decrypted(struct sock *sk, struct sk_buff *skb)
+{
+        struct tls_context *tls_ctx = tls_get_ctx(sk);
+        struct tls_offload_context_rx *ctx = tls_offload_ctx_rx(tls_ctx);
+        int is_decrypted = skb->decrypted;
+        int is_encrypted = !is_decrypted;
+        struct sk_buff *skb_iter;
+
+        /* Skip if it is already decrypted */
+        if (ctx->sw.decrypted)
+                return 0;
+
+        /* Check if all the data is decrypted already */
+        skb_walk_frags(skb, skb_iter) {
+                is_decrypted &= skb_iter->decrypted;
+                is_encrypted &= !skb_iter->decrypted;
+        }
+
+        ctx->sw.decrypted |= is_decrypted;
+
+        /* Return immedeatly if the record is either entirely plaintext or
+         * entirely ciphertext. Otherwise handle reencrypt partially decrypted
+         * record.
+         */
+        return (is_encrypted || is_decrypted) ? 0 :
+                tls_device_reencrypt(sk, skb);
+}
+
 int tls_set_device_offload(struct sock *sk, struct tls_context *ctx)
 {
         u16 nonce_size, tag_size, iv_size, rec_seq_size;
@@ -608,7 +743,6 @@ int tls_set_device_offload(struct sock *sk, struct tls_context *ctx)
 
         clean_acked_data_enable(inet_csk(sk), &tls_icsk_clean_acked);
         ctx->push_pending_record = tls_device_push_pending_record;
-        offload_ctx->sk_destruct = sk->sk_destruct;
 
         /* TLS offload is greatly simplified if we don't send
          * SKBs where only part of the payload needs to be encrypted.
@@ -618,8 +752,6 @@ int tls_set_device_offload(struct sock *sk, struct tls_context *ctx)
         if (skb)
                 TCP_SKB_CB(skb)->eor = 1;
 
-        refcount_set(&ctx->refcount, 1);
-
         /* We support starting offload on multiple sockets
          * concurrently, so we only need a read lock here.
          * This lock must precede get_netdev_for_sock to prevent races between
@@ -654,19 +786,14 @@ int tls_set_device_offload(struct sock *sk, struct tls_context *ctx)
         if (rc)
                 goto release_netdev;
 
-        ctx->netdev = netdev;
+        tls_device_attach(ctx, sk, netdev);
 
-        spin_lock_irq(&tls_device_lock);
-        list_add_tail(&ctx->list, &tls_device_list);
-        spin_unlock_irq(&tls_device_lock);
-
-        sk->sk_validate_xmit_skb = tls_validate_xmit_skb;
         /* following this assignment tls_is_sk_tx_device_offloaded
          * will return true and the context might be accessed
          * by the netdev's xmit function.
          */
-        smp_store_release(&sk->sk_destruct,
-                          &tls_device_sk_destruct);
+        smp_store_release(&sk->sk_validate_xmit_skb, tls_validate_xmit_skb);
+        dev_put(netdev);
         up_read(&device_offload_lock);
         goto out;
 
@@ -689,6 +816,105 @@ out:
         return rc;
 }
 
+int tls_set_device_offload_rx(struct sock *sk, struct tls_context *ctx)
+{
+        struct tls_offload_context_rx *context;
+        struct net_device *netdev;
+        int rc = 0;
+
+        /* We support starting offload on multiple sockets
+         * concurrently, so we only need a read lock here.
+         * This lock must precede get_netdev_for_sock to prevent races between
+         * NETDEV_DOWN and setsockopt.
+         */
+        down_read(&device_offload_lock);
+        netdev = get_netdev_for_sock(sk);
+        if (!netdev) {
+                pr_err_ratelimited("%s: netdev not found\n", __func__);
+                rc = -EINVAL;
+                goto release_lock;
+        }
+
+        if (!(netdev->features & NETIF_F_HW_TLS_RX)) {
+                pr_err_ratelimited("%s: netdev %s with no TLS offload\n",
+                                   __func__, netdev->name);
+                rc = -ENOTSUPP;
+                goto release_netdev;
+        }
+
+        /* Avoid offloading if the device is down
+         * We don't want to offload new flows after
+         * the NETDEV_DOWN event
+         */
+        if (!(netdev->flags & IFF_UP)) {
+                rc = -EINVAL;
+                goto release_netdev;
+        }
+
+        context = kzalloc(TLS_OFFLOAD_CONTEXT_SIZE_RX, GFP_KERNEL);
+        if (!context) {
+                rc = -ENOMEM;
+                goto release_netdev;
+        }
+
+        ctx->priv_ctx_rx = context;
+        rc = tls_set_sw_offload(sk, ctx, 0);
+        if (rc)
+                goto release_ctx;
+
+        rc = netdev->tlsdev_ops->tls_dev_add(netdev, sk, TLS_OFFLOAD_CTX_DIR_RX,
+                                             &ctx->crypto_recv,
+                                             tcp_sk(sk)->copied_seq);
+        if (rc) {
+                pr_err_ratelimited("%s: The netdev has refused to offload this socket\n",
+                                   __func__);
+                goto free_sw_resources;
+        }
+
+        tls_device_attach(ctx, sk, netdev);
+        goto release_netdev;
+
+free_sw_resources:
+        tls_sw_free_resources_rx(sk);
+release_ctx:
+        ctx->priv_ctx_rx = NULL;
+release_netdev:
+        dev_put(netdev);
+release_lock:
+        up_read(&device_offload_lock);
+        return rc;
+}
+
+void tls_device_offload_cleanup_rx(struct sock *sk)
+{
+        struct tls_context *tls_ctx = tls_get_ctx(sk);
+        struct net_device *netdev;
+
+        down_read(&device_offload_lock);
+        netdev = tls_ctx->netdev;
+        if (!netdev)
+                goto out;
+
+        if (!(netdev->features & NETIF_F_HW_TLS_RX)) {
+                pr_err_ratelimited("%s: device is missing NETIF_F_HW_TLS_RX cap\n",
+                                   __func__);
+                goto out;
+        }
+
+        netdev->tlsdev_ops->tls_dev_del(netdev, tls_ctx,
+                                        TLS_OFFLOAD_CTX_DIR_RX);
+
+        if (tls_ctx->tx_conf != TLS_HW) {
+                dev_put(netdev);
+                tls_ctx->netdev = NULL;
+        }
+out:
+        up_read(&device_offload_lock);
+        kfree(tls_ctx->rx.rec_seq);
+        kfree(tls_ctx->rx.iv);
+        tls_sw_release_resources_rx(sk);
+}
+
 static int tls_device_down(struct net_device *netdev)
 {
         struct tls_context *ctx, *tmp;
@@ -709,8 +935,12 @@ static int tls_device_down(struct net_device *netdev)
         spin_unlock_irqrestore(&tls_device_lock, flags);
 
         list_for_each_entry_safe(ctx, tmp, &list, list) {
-                netdev->tlsdev_ops->tls_dev_del(netdev, ctx,
-                                                TLS_OFFLOAD_CTX_DIR_TX);
+                if (ctx->tx_conf == TLS_HW)
+                        netdev->tlsdev_ops->tls_dev_del(netdev, ctx,
+                                                        TLS_OFFLOAD_CTX_DIR_TX);
+                if (ctx->rx_conf == TLS_HW)
+                        netdev->tlsdev_ops->tls_dev_del(netdev, ctx,
+                                                        TLS_OFFLOAD_CTX_DIR_RX);
                 ctx->netdev = NULL;
                 dev_put(netdev);
                 list_del_init(&ctx->list);
@@ -731,12 +961,16 @@ static int tls_dev_event(struct notifier_block *this, unsigned long event,
 {
         struct net_device *dev = netdev_notifier_info_to_dev(ptr);
 
-        if (!(dev->features & NETIF_F_HW_TLS_TX))
+        if (!(dev->features & (NETIF_F_HW_TLS_RX | NETIF_F_HW_TLS_TX)))
                 return NOTIFY_DONE;
 
         switch (event) {
         case NETDEV_REGISTER:
         case NETDEV_FEAT_CHANGE:
+                if ((dev->features & NETIF_F_HW_TLS_RX) &&
+                    !dev->tlsdev_ops->tls_dev_resync_rx)
+                        return NOTIFY_BAD;
+
                 if  (dev->tlsdev_ops &&
                      dev->tlsdev_ops->tls_dev_add &&
                      dev->tlsdev_ops->tls_dev_del)