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[Openvpn-devel] [PATCH ovpn v2] ovpn: consolidate crypto allocations in one chunk
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From: Ralf L. <ra...@ma...> - 2025-11-13 12:40:56
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Currently ovpn uses three separate dynamically allocated structures to
set up cryptographic operations for both encryption and decryption. This
adds overhead to performance-critical paths and contribute to memory
fragmentation.
This commit consolidates those allocations into a single temporary blob,
similar to what esp_alloc_tmp() does.
The resulting performance gain is +7.7% and +4.3% for UDP when using AES
and ChaChaPoly respectively, and +4.3% for TCP.
Signed-off-by: Ralf Lici <ra...@ma...>
Signed-off-by: Antonio Quartulli <an...@op...>
---
Changes since v1:
- Fixed typo in commit message
- Adjusted ovpn_aead_crypto_tmp_size comment to follow kdoc style
- Stored allocated blob in the skb control block immediately after
allocation to prevent leakage on failure
drivers/net/ovpn/crypto_aead.c | 155 +++++++++++++++++++++++++--------
drivers/net/ovpn/io.c | 8 +-
drivers/net/ovpn/skb.h | 13 ++-
3 files changed, 131 insertions(+), 45 deletions(-)
diff --git a/drivers/net/ovpn/crypto_aead.c b/drivers/net/ovpn/crypto_aead.c
index cb6cdf8ec317..6b55d2e715bc 100644
--- a/drivers/net/ovpn/crypto_aead.c
+++ b/drivers/net/ovpn/crypto_aead.c
@@ -36,6 +36,105 @@ static int ovpn_aead_encap_overhead(const struct ovpn_crypto_key_slot *ks)
crypto_aead_authsize(ks->encrypt); /* Auth Tag */
}
+/**
+ * ovpn_aead_crypto_tmp_size - compute the size of a temporary object containing
+ * an AEAD request structure with extra space for SG
+ * and IV.
+ * @tfm: the AEAD cipher handle
+ * @nfrags: the number of fragments in the skb
+ *
+ * This function calculates the size of a contiguous memory block that includes
+ * the initialization vector (IV), the AEAD request, and an array of scatterlist
+ * entries. For alignment considerations, the IV is placed first, followed by
+ * the request, and then the scatterlist.
+ * Additional alignment is applied according to the requirements of the
+ * underlying structures.
+ *
+ * Return: the size of the temporary memory that needs to be allocated
+ */
+static unsigned int ovpn_aead_crypto_tmp_size(struct crypto_aead *tfm,
+ const unsigned int nfrags)
+{
+ unsigned int len = crypto_aead_ivsize(tfm);
+
+ if (likely(len)) {
+ /* min size for a buffer of ivsize, aligned to alignmask */
+ len += crypto_aead_alignmask(tfm) &
+ ~(crypto_tfm_ctx_alignment() - 1);
+ /* round up to the next multiple of the crypto ctx alignment */
+ len = ALIGN(len, crypto_tfm_ctx_alignment());
+ }
+
+ /* reserve space for the AEAD request */
+ len += sizeof(struct aead_request) + crypto_aead_reqsize(tfm);
+ /* round up to the next multiple of the scatterlist alignment */
+ len = ALIGN(len, __alignof__(struct scatterlist));
+
+ /* add enough space for nfrags + 2 scatterlist entries */
+ len += sizeof(struct scatterlist) * (nfrags + 2);
+ return len;
+}
+
+/**
+ * ovpn_aead_crypto_tmp_iv - retrieve the pointer to the IV within a temporary
+ * buffer allocated using ovpn_aead_crypto_tmp_size
+ * @aead: the AEAD cipher handle
+ * @tmp: a pointer to the beginning of the temporary buffer
+ *
+ * This function retrieves a pointer to the initialization vector (IV) in the
+ * temporary buffer. If the AEAD cipher specifies an IV size, the pointer is
+ * adjusted using the AEAD's alignment mask to ensure proper alignment.
+ *
+ * Returns: a pointer to the IV within the temporary buffer
+ */
+static u8 *ovpn_aead_crypto_tmp_iv(struct crypto_aead *aead, void *tmp)
+{
+ return likely(crypto_aead_ivsize(aead)) ?
+ PTR_ALIGN((u8 *)tmp, crypto_aead_alignmask(aead) + 1) :
+ tmp;
+}
+
+/**
+ * ovpn_aead_crypto_tmp_req - retrieve the pointer to the AEAD request structure
+ * within a temporary buffer allocated using
+ * ovpn_aead_crypto_tmp_size
+ * @aead: the AEAD cipher handle
+ * @iv: a pointer to the initialization vector in the temporary buffer
+ *
+ * This function computes the location of the AEAD request structure that
+ * immediately follows the IV in the temporary buffer and it ensures the request
+ * is aligned to the crypto transform context alignment.
+ *
+ * Returns: a pointer to the AEAD request structure
+ */
+static struct aead_request *ovpn_aead_crypto_tmp_req(struct crypto_aead *aead,
+ const u8 *iv)
+{
+ return (void *)PTR_ALIGN(iv + crypto_aead_ivsize(aead),
+ crypto_tfm_ctx_alignment());
+}
+
+/**
+ * ovpn_aead_crypto_req_sg - locate the scatterlist following the AEAD request
+ * within a temporary buffer allocated using
+ * ovpn_aead_crypto_tmp_size
+ * @aead: the AEAD cipher handle
+ * @req: a pointer to the AEAD request structure in the temporary buffer
+ *
+ * This function computes the starting address of the scatterlist that is
+ * allocated immediately after the AEAD request structure. It aligns the pointer
+ * based on the alignment requirements of the scatterlist structure.
+ *
+ * Returns: a pointer to the scatterlist
+ */
+static struct scatterlist *ovpn_aead_crypto_req_sg(struct crypto_aead *aead,
+ struct aead_request *req)
+{
+ return (void *)ALIGN((unsigned long)(req + 1) +
+ crypto_aead_reqsize(aead),
+ __alignof__(struct scatterlist));
+}
+
int ovpn_aead_encrypt(struct ovpn_peer *peer, struct ovpn_crypto_key_slot *ks,
struct sk_buff *skb)
{
@@ -45,6 +144,7 @@ int ovpn_aead_encrypt(struct ovpn_peer *peer, struct ovpn_crypto_key_slot *ks,
struct scatterlist *sg;
int nfrags, ret;
u32 pktid, op;
+ void *tmp;
u8 *iv;
ovpn_skb_cb(skb)->peer = peer;
@@ -71,13 +171,17 @@ int ovpn_aead_encrypt(struct ovpn_peer *peer, struct ovpn_crypto_key_slot *ks,
if (unlikely(nfrags + 2 > (MAX_SKB_FRAGS + 2)))
return -ENOSPC;
- /* sg may be required by async crypto */
- ovpn_skb_cb(skb)->sg = kmalloc(sizeof(*ovpn_skb_cb(skb)->sg) *
- (nfrags + 2), GFP_ATOMIC);
- if (unlikely(!ovpn_skb_cb(skb)->sg))
+ /* allocate temporary memory for iv, sg and req */
+ tmp = kmalloc(ovpn_aead_crypto_tmp_size(ks->encrypt, nfrags),
+ GFP_ATOMIC);
+ if (unlikely(!tmp))
return -ENOMEM;
- sg = ovpn_skb_cb(skb)->sg;
+ ovpn_skb_cb(skb)->crypto_tmp = tmp;
+
+ iv = ovpn_aead_crypto_tmp_iv(ks->encrypt, tmp);
+ req = ovpn_aead_crypto_tmp_req(ks->encrypt, iv);
+ sg = ovpn_aead_crypto_req_sg(ks->encrypt, req);
/* sg table:
* 0: op, wire nonce (AD, len=OVPN_OP_SIZE_V2+OVPN_NONCE_WIRE_SIZE),
@@ -105,13 +209,6 @@ int ovpn_aead_encrypt(struct ovpn_peer *peer, struct ovpn_crypto_key_slot *ks,
if (unlikely(ret < 0))
return ret;
- /* iv may be required by async crypto */
- ovpn_skb_cb(skb)->iv = kmalloc(OVPN_NONCE_SIZE, GFP_ATOMIC);
- if (unlikely(!ovpn_skb_cb(skb)->iv))
- return -ENOMEM;
-
- iv = ovpn_skb_cb(skb)->iv;
-
/* concat 4 bytes packet id and 8 bytes nonce tail into 12 bytes
* nonce
*/
@@ -130,12 +227,6 @@ int ovpn_aead_encrypt(struct ovpn_peer *peer, struct ovpn_crypto_key_slot *ks,
/* AEAD Additional data */
sg_set_buf(sg, skb->data, OVPN_AAD_SIZE);
- req = aead_request_alloc(ks->encrypt, GFP_ATOMIC);
- if (unlikely(!req))
- return -ENOMEM;
-
- ovpn_skb_cb(skb)->req = req;
-
/* setup async crypto operation */
aead_request_set_tfm(req, ks->encrypt);
aead_request_set_callback(req, 0, ovpn_encrypt_post, skb);
@@ -156,6 +247,7 @@ int ovpn_aead_decrypt(struct ovpn_peer *peer, struct ovpn_crypto_key_slot *ks,
struct aead_request *req;
struct sk_buff *trailer;
struct scatterlist *sg;
+ void *tmp;
u8 *iv;
payload_offset = OVPN_AAD_SIZE + tag_size;
@@ -184,13 +276,17 @@ int ovpn_aead_decrypt(struct ovpn_peer *peer, struct ovpn_crypto_key_slot *ks,
if (unlikely(nfrags + 2 > (MAX_SKB_FRAGS + 2)))
return -ENOSPC;
- /* sg may be required by async crypto */
- ovpn_skb_cb(skb)->sg = kmalloc(sizeof(*ovpn_skb_cb(skb)->sg) *
- (nfrags + 2), GFP_ATOMIC);
- if (unlikely(!ovpn_skb_cb(skb)->sg))
+ /* allocate temporary memory for iv, sg and req */
+ tmp = kmalloc(ovpn_aead_crypto_tmp_size(ks->decrypt, nfrags),
+ GFP_ATOMIC);
+ if (unlikely(!tmp))
return -ENOMEM;
- sg = ovpn_skb_cb(skb)->sg;
+ ovpn_skb_cb(skb)->crypto_tmp = tmp;
+
+ iv = ovpn_aead_crypto_tmp_iv(ks->decrypt, tmp);
+ req = ovpn_aead_crypto_tmp_req(ks->decrypt, iv);
+ sg = ovpn_aead_crypto_req_sg(ks->decrypt, req);
/* sg table:
* 0: op, wire nonce (AD, len=OVPN_OPCODE_SIZE+OVPN_NONCE_WIRE_SIZE),
@@ -213,24 +309,11 @@ int ovpn_aead_decrypt(struct ovpn_peer *peer, struct ovpn_crypto_key_slot *ks,
/* append auth_tag onto scatterlist */
sg_set_buf(sg + ret + 1, skb->data + OVPN_AAD_SIZE, tag_size);
- /* iv may be required by async crypto */
- ovpn_skb_cb(skb)->iv = kmalloc(OVPN_NONCE_SIZE, GFP_ATOMIC);
- if (unlikely(!ovpn_skb_cb(skb)->iv))
- return -ENOMEM;
-
- iv = ovpn_skb_cb(skb)->iv;
-
/* copy nonce into IV buffer */
memcpy(iv, skb->data + OVPN_OPCODE_SIZE, OVPN_NONCE_WIRE_SIZE);
memcpy(iv + OVPN_NONCE_WIRE_SIZE, ks->nonce_tail_recv,
OVPN_NONCE_TAIL_SIZE);
- req = aead_request_alloc(ks->decrypt, GFP_ATOMIC);
- if (unlikely(!req))
- return -ENOMEM;
-
- ovpn_skb_cb(skb)->req = req;
-
/* setup async crypto operation */
aead_request_set_tfm(req, ks->decrypt);
aead_request_set_callback(req, 0, ovpn_decrypt_post, skb);
diff --git a/drivers/net/ovpn/io.c b/drivers/net/ovpn/io.c
index 3e9e7f8444b3..2721ee8268b2 100644
--- a/drivers/net/ovpn/io.c
+++ b/drivers/net/ovpn/io.c
@@ -119,9 +119,7 @@ void ovpn_decrypt_post(void *data, int ret)
peer = ovpn_skb_cb(skb)->peer;
/* crypto is done, cleanup skb CB and its members */
- kfree(ovpn_skb_cb(skb)->iv);
- kfree(ovpn_skb_cb(skb)->sg);
- aead_request_free(ovpn_skb_cb(skb)->req);
+ kfree(ovpn_skb_cb(skb)->crypto_tmp);
if (unlikely(ret < 0))
goto drop;
@@ -248,9 +246,7 @@ void ovpn_encrypt_post(void *data, int ret)
peer = ovpn_skb_cb(skb)->peer;
/* crypto is done, cleanup skb CB and its members */
- kfree(ovpn_skb_cb(skb)->iv);
- kfree(ovpn_skb_cb(skb)->sg);
- aead_request_free(ovpn_skb_cb(skb)->req);
+ kfree(ovpn_skb_cb(skb)->crypto_tmp);
if (unlikely(ret == -ERANGE)) {
/* we ran out of IVs and we must kill the key as it can't be
diff --git a/drivers/net/ovpn/skb.h b/drivers/net/ovpn/skb.h
index 64430880f1da..4fb7ea025426 100644
--- a/drivers/net/ovpn/skb.h
+++ b/drivers/net/ovpn/skb.h
@@ -18,12 +18,19 @@
#include <linux/socket.h>
#include <linux/types.h>
+/**
+ * struct ovpn_cb - ovpn skb control block
+ * @peer: the peer this skb was received from/sent to
+ * @ks: the crypto key slot used to encrypt/decrypt this skb
+ * @crypto_tmp: pointer to temporary memory used for crypto operations
+ * containing the IV, the scatter gather list and the aead request
+ * @payload_offset: offset in the skb where the payload starts
+ * @nosignal: whether this skb should be sent with the MSG_NOSIGNAL flag (TCP)
+ */
struct ovpn_cb {
struct ovpn_peer *peer;
struct ovpn_crypto_key_slot *ks;
- struct aead_request *req;
- struct scatterlist *sg;
- u8 *iv;
+ void *crypto_tmp;
unsigned int payload_offset;
bool nosignal;
};
--
2.51.1
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