Re: [PATCH net-next v3 1/8] netdevsim: a basic test PSP implementation

Jakub Kicinski wrote:

Provide a PSP implementation for netdevsim.

Use psp_dev_encapsulate() and psp_dev_rcv() to do actual encapsulation and decapsulation on skbs, but perform no encryption or decryption. In order to make encryption with a bad key result in a drop on the peer's rx side, we stash our psd's generation number in the first byte of each key before handing to the peer.

Signed-off-by: Jakub Kicinski kuba@kernel.org Co-developed-by: Daniel Zahka daniel.zahka@gmail.com Signed-off-by: Daniel Zahka daniel.zahka@gmail.com

---

v3:

• fix init error path
• fix unused variable with ipv6=n (__maybe_unused, all options seem equally bad here)

---

drivers/net/netdevsim/Makefile | 4 + drivers/net/netdevsim/netdevsim.h | 27 ++++ drivers/net/netdevsim/netdev.c | 43 +++++- drivers/net/netdevsim/psp.c | 225 ++++++++++++++++++++++++++++++ net/core/skbuff.c | 1 + 5 files changed, 294 insertions(+), 6 deletions(-) create mode 100644 drivers/net/netdevsim/psp.c

diff --git a/drivers/net/netdevsim/Makefile b/drivers/net/netdevsim/Makefile index f8de93bc5f5b..14a553e000ec 100644 --- a/drivers/net/netdevsim/Makefile +++ b/drivers/net/netdevsim/Makefile @@ -18,6 +18,10 @@ ifneq ($(CONFIG_PSAMPLE),) netdevsim-objs += psample.o endif +ifneq ($(CONFIG_INET_PSP),) +netdevsim-objs += psp.o +endif

ifneq ($(CONFIG_MACSEC),) netdevsim-objs += macsec.o endif diff --git a/drivers/net/netdevsim/netdevsim.h b/drivers/net/netdevsim/netdevsim.h index bddd24c1389d..02c1c97b7008 100644 --- a/drivers/net/netdevsim/netdevsim.h +++ b/drivers/net/netdevsim/netdevsim.h @@ -108,6 +108,12 @@ struct netdevsim { int rq_reset_mode;

• struct {

• struct psp_dev *dev;
  

• u32 spi;
  

• u32 assoc_cnt;
  

• } psp;
• struct nsim_bus_dev *nsim_bus_dev;

struct bpf_prog *bpf_offloaded; @@ -421,6 +427,27 @@ static inline void nsim_macsec_teardown(struct netdevsim *ns) } #endif +#if IS_ENABLED(CONFIG_INET_PSP) +int nsim_psp_init(struct netdevsim *ns); +void nsim_psp_uninit(struct netdevsim *ns); +void nsim_psp_handle_ext(struct sk_buff *skb, struct skb_ext *psp_ext); +enum skb_drop_reason +nsim_do_psp(struct sk_buff *skb, struct netdevsim *ns,

•    struct netdevsim *peer_ns, struct skb_ext **psp_ext);
  

+#else +static inline int nsim_psp_init(struct netdevsim *ns) { return 0; } +static inline void nsim_psp_uninit(struct netdevsim *ns) {} +static inline enum skb_drop_reason +nsim_do_psp(struct sk_buff *skb, struct netdevsim *ns,

•    struct netdevsim *peer_ns, struct skb_ext **psp_ext)
  

+{

• return 0;

+}

+static inline void +nsim_psp_handle_ext(struct sk_buff *skb, struct skb_ext *psp_ext) {} +#endif

struct nsim_bus_dev { struct device dev; struct list_head list; diff --git a/drivers/net/netdevsim/netdev.c b/drivers/net/netdevsim/netdev.c index 0178219f0db5..ebc3833e95b4 100644 --- a/drivers/net/netdevsim/netdev.c +++ b/drivers/net/netdevsim/netdev.c @@ -103,28 +103,42 @@ static int nsim_napi_rx(struct net_device *tx_dev, struct net_device *rx_dev, static int nsim_forward_skb(struct net_device *tx_dev, struct net_device *rx_dev, struct sk_buff *skb,

• 	    struct nsim_rq *rq)
  

• 	    struct nsim_rq *rq,
  

• 	    struct skb_ext *psp_ext)
  

{

• return __dev_forward_skb(rx_dev, skb) ?:

• nsim_napi_rx(tx_dev, rx_dev, rq, skb);
  

• int ret;
• ret = __dev_forward_skb(rx_dev, skb);
• if (ret)

• return ret;
  

• nsim_psp_handle_ext(skb, psp_ext);
• return nsim_napi_rx(tx_dev, rx_dev, rq, skb);

} static netdev_tx_t nsim_start_xmit(struct sk_buff *skb, struct net_device *dev) { struct netdevsim *ns = netdev_priv(dev);

• struct skb_ext *psp_ext = NULL; struct net_device *peer_dev; unsigned int len = skb->len; struct netdevsim *peer_ns; struct netdev_config *cfg; struct nsim_rq *rq; int rxq;
• int dr;

rcu_read_lock(); if (!nsim_ipsec_tx(ns, skb))

• goto out_drop_free;
  

• goto out_drop_any;
  

peer_ns = rcu_dereference(ns->peer); if (!peer_ns)

• goto out_drop_any;
  

• dr = nsim_do_psp(skb, ns, peer_ns, &psp_ext);
• if (dr) goto out_drop_free;

peer_dev = peer_ns->netdev; @@ -141,7 +155,8 @@ static netdev_tx_t nsim_start_xmit(struct sk_buff *skb, struct net_device *dev) skb_linearize(skb); skb_tx_timestamp(skb);

• if (unlikely(nsim_forward_skb(dev, peer_dev, skb, rq) == NET_RX_DROP))

• if (unlikely(nsim_forward_skb(dev, peer_dev,

• 		      skb, rq, psp_ext) == NET_RX_DROP))
  

  goto out_drop_cnt;

if (!hrtimer_active(&rq->napi_timer)) @@ -151,8 +166,10 @@ static netdev_tx_t nsim_start_xmit(struct sk_buff *skb, struct net_device *dev) dev_dstats_tx_add(dev, len); return NETDEV_TX_OK; +out_drop_any:

• dr = SKB_DROP_REASON_NOT_SPECIFIED;

out_drop_free:

• dev_kfree_skb(skb);

• kfree_skb_reason(skb, dr);

out_drop_cnt: rcu_read_unlock(); dev_dstats_tx_dropped(dev); @@ -1002,6 +1019,7 @@ static void nsim_queue_uninit(struct netdevsim *ns) static int nsim_init_netdevsim(struct netdevsim *ns) {

• struct netdevsim *peer; struct mock_phc *phc; int err;

@@ -1036,6 +1054,10 @@ static int nsim_init_netdevsim(struct netdevsim *ns) goto err_ipsec_teardown; rtnl_unlock();

• err = nsim_psp_init(ns);
• if (err)

• goto err_unregister_netdev;
  

• if (IS_ENABLED(CONFIG_DEBUG_NET)) { ns->nb.notifier_call = netdev_debug_event; if (register_netdevice_notifier_dev_net(ns->netdev, &ns->nb,

@@ -1045,6 +1067,13 @@ static int nsim_init_netdevsim(struct netdevsim *ns) return 0; +err_unregister_netdev:

• rtnl_lock();
• peer = rtnl_dereference(ns->peer);
• if (peer)

• RCU_INIT_POINTER(peer->peer, NULL);
  

• RCU_INIT_POINTER(ns->peer, NULL);
• unregister_netdevice(ns->netdev);

Could maybe use a shared helper with the same logic in nsim_destroy

err_ipsec_teardown: nsim_ipsec_teardown(ns); nsim_macsec_teardown(ns); @@ -1132,6 +1161,8 @@ void nsim_destroy(struct netdevsim *ns) unregister_netdevice_notifier_dev_net(ns->netdev, &ns->nb, &ns->nn);

• nsim_psp_uninit(ns);
• rtnl_lock(); peer = rtnl_dereference(ns->peer); if (peer)

diff --git a/drivers/net/netdevsim/psp.c b/drivers/net/netdevsim/psp.c new file mode 100644 index 000000000000..332b5b744f01 --- /dev/null +++ b/drivers/net/netdevsim/psp.c @@ -0,0 +1,225 @@ +// SPDX-License-Identifier: GPL-2.0

+#include <linux/ip.h> +#include <linux/skbuff.h> +#include <net/ip6_checksum.h> +#include <net/psp.h> +#include <net/sock.h>

+#include "netdevsim.h"

+void nsim_psp_handle_ext(struct sk_buff *skb, struct skb_ext *psp_ext) +{

• if (psp_ext)

• __skb_ext_set(skb, SKB_EXT_PSP, psp_ext);
  

+}

+enum skb_drop_reason +nsim_do_psp(struct sk_buff *skb, struct netdevsim *ns,

•    struct netdevsim *peer_ns, struct skb_ext **psp_ext)
  

+{

• enum skb_drop_reason rc = 0;
• struct psp_assoc *pas;
• struct net *net;
• void **ptr;
• rcu_read_lock();
• pas = psp_skb_get_assoc_rcu(skb);
• if (!pas) {

• rc = SKB_NOT_DROPPED_YET;
  

• goto out_unlock;
  

• }
• if (!skb_transport_header_was_set(skb)) {

• rc = SKB_DROP_REASON_PSP_OUTPUT;
  

• goto out_unlock;
  

• }
• ptr = psp_assoc_drv_data(pas);
• if (*ptr != ns) {

• rc = SKB_DROP_REASON_PSP_OUTPUT;
  

• goto out_unlock;
  

• }
• net = sock_net(skb->sk);
• if (!psp_dev_encapsulate(net, skb, pas->tx.spi, pas->version, 0)) {

• rc = SKB_DROP_REASON_PSP_OUTPUT;
  

• goto out_unlock;
  

• }
• /* Now pretend we just received this frame */
• if (peer_ns->psp.dev->config.versions & (1 << pas->version)) {

• bool strip_icv = false;
  

Here for readability? Never modified, could be dropped.

• u8 generation;
  

• /* We cheat a bit and put the generation in the key.
  

•  * In real life if generation was too old, then decryption would
  

•  * fail. Here, we just make it so a bad key causes a bad
  

•  * generation too, and psp_sk_rx_policy_check() will fail.
  

•  */
  

• generation = pas->tx.key[0];
  

• skb_ext_reset(skb);
  

• skb->mac_len = ETH_HLEN;
  

• if (psp_dev_rcv(skb, peer_ns->psp.dev->id, generation,
  

• 		strip_icv)) {
  

• 	rc = SKB_DROP_REASON_PSP_OUTPUT;
  

• 	goto out_unlock;
  

• }
  

• *psp_ext = skb->extensions;
  

• refcount_inc(&(*psp_ext)->refcnt);
  

• skb->decrypted = 1;
  

• } else {

• struct ipv6hdr *ip6h __maybe_unused;
  

• struct iphdr *iph;
  

• struct udphdr *uh;
  

• __wsum csum;
  

• /* Do not decapsulate. Receive the skb with the udp and psp
  

•  * headers still there as if this is a normal udp packet.
  

•  * psp_dev_encapsulate() sets udp checksum to 0, so we need to
  

•  * provide a valid checksum here, so the skb isn't dropped.
  

•  */
  

• uh = udp_hdr(skb);
  

• csum = skb_checksum(skb, skb_transport_offset(skb),
  

• 		    ntohs(uh->len), 0);
  

• switch (skb->protocol) {
  

• case htons(ETH_P_IP):
  

• 	iph = ip_hdr(skb);
  

• 	uh->check = udp_v4_check(ntohs(uh->len), iph->saddr,
  

• 				 iph->daddr, csum);
  

• 	break;
  

+#if IS_ENABLED(CONFIG_IPV6)

• case htons(ETH_P_IPV6):
  

• 	ip6h = ipv6_hdr(skb);
  

• 	uh->check = udp_v6_check(ntohs(uh->len), &ip6h->saddr,
  

• 				 &ip6h->daddr, csum);
  

• 	break;
  

+#endif

• }
  

• uh->check	= uh->check ?: CSUM_MANGLED_0;
  

• skb->ip_summed	= CHECKSUM_NONE;
  

Could just set CHECKSUM_UNNECESSARY and forgo the checksum calculation?