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 <[email protected]>
> Co-developed-by: Daniel Zahka <[email protected]>
> Signed-off-by: Daniel Zahka <[email protected]>
> ---
> 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?
