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Date: Wed, 2 Oct 2019 08:58:52 -0700
From: Roopa Prabhu <roopa@...ulusnetworks.com>
To: Ido Schimmel <idosch@...sch.org>
Cc: netdev <netdev@...r.kernel.org>,
David Miller <davem@...emloft.net>,
David Ahern <dsahern@...il.com>,
Jiri Pirko <jiri@...lanox.com>,
Jakub Kicinski <jakub.kicinski@...ronome.com>,
Saeed Mahameed <saeedm@...lanox.com>,
mlxsw <mlxsw@...lanox.com>, Ido Schimmel <idosch@...lanox.com>
Subject: Re: [RFC PATCH net-next 12/15] ipv4: Add "in hardware" indication to routes
On Wed, Oct 2, 2019 at 1:41 AM Ido Schimmel <idosch@...sch.org> wrote:
>
> From: Ido Schimmel <idosch@...lanox.com>
>
> When performing L3 offload, routes and nexthops are usually programmed
> into two different tables in the underlying device. Therefore, the fact
> that a nexthop resides in hardware does not necessarily mean that all
> the associated routes also reside in hardware and vice-versa.
>
> While the kernel can signal to user space the presence of a nexthop in
> hardware (via 'RTNH_F_OFFLOAD'), it does not have a corresponding flag
> for routes. In addition, the fact that a route resides in hardware does
> not necessarily mean that the traffic is offloaded. For example,
> unreachable routes (i.e., 'RTN_UNREACHABLE') are programmed to trap
> packets to the CPU so that the kernel will be able to generate the
> appropriate ICMP error packet.
>
> This patch adds an "in hardware" indication to IPv4 routes, so that
> users will have better visibility into the offload process. In the
> future IPv6 will be extended with this indication as well.
>
> 'struct fib_alias' is extended with a new field that indicates if
> the route resides in hardware or not. Note that the new field is added
> in the 6 bytes hole and therefore the struct still fits in a single
> cache line [1].
>
> Capable drivers are expected to invoke fib_alias_in_hw_{set,clear}()
> with the route's key in order to set / clear the "in hardware
> indication".
>
> The new indication is dumped to user space via a new flag (i.e.,
> 'RTM_F_IN_HW') in the 'rtm_flags' field in the ancillary header.
>
nice series Ido. why not call this RTM_F_OFFLOAD to keep it consistent
with the nexthop offload indication ?.
But this again does not seem to be similar to the other request flags
like: RTM_F_FIB_MATCH
(so far i think all the RTNH_F_* flags are used on routes too IIRC
(see iproute2: print_rt_flags)
RTNH_F_DEAD seems to fall in this category)
> [1]
> struct fib_alias {
> struct hlist_node fa_list; /* 0 16 */
> struct fib_info * fa_info; /* 16 8 */
> u8 fa_tos; /* 24 1 */
> u8 fa_type; /* 25 1 */
> u8 fa_state; /* 26 1 */
> u8 fa_slen; /* 27 1 */
> u32 tb_id; /* 28 4 */
> s16 fa_default; /* 32 2 */
> u8 in_hw:1; /* 34: 0 1 */
> u8 unused:7; /* 34: 1 1 */
>
> /* XXX 5 bytes hole, try to pack */
>
> struct callback_head rcu __attribute__((__aligned__(8))); /* 40 16 */
>
> /* size: 56, cachelines: 1, members: 11 */
> /* sum members: 50, holes: 1, sum holes: 5 */
> /* sum bitfield members: 8 bits (1 bytes) */
> /* forced alignments: 1, forced holes: 1, sum forced holes: 5 */
> /* last cacheline: 56 bytes */
> } __attribute__((__aligned__(8)));
>
> Signed-off-by: Ido Schimmel <idosch@...lanox.com>
> ---
> include/net/ip_fib.h | 5 +++
> include/uapi/linux/rtnetlink.h | 1 +
> net/ipv4/fib_lookup.h | 4 ++
> net/ipv4/fib_semantics.c | 4 ++
> net/ipv4/fib_trie.c | 71 ++++++++++++++++++++++++++++++++++
> 5 files changed, 85 insertions(+)
>
> diff --git a/include/net/ip_fib.h b/include/net/ip_fib.h
> index 52b2406a5dfc..019a138a79f4 100644
> --- a/include/net/ip_fib.h
> +++ b/include/net/ip_fib.h
> @@ -454,6 +454,11 @@ int fib_nh_common_init(struct fib_nh_common *nhc, struct nlattr *fc_encap,
> void fib_nh_common_release(struct fib_nh_common *nhc);
>
> /* Exported by fib_trie.c */
> +void fib_alias_in_hw_set(struct net *net, u32 dst, int dst_len,
> + const struct fib_info *fi, u8 tos, u8 type, u32 tb_id);
> +void fib_alias_in_hw_clear(struct net *net, u32 dst, int dst_len,
> + const struct fib_info *fi, u8 tos, u8 type,
> + u32 tb_id);
> void fib_trie_init(void);
> struct fib_table *fib_trie_table(u32 id, struct fib_table *alias);
>
> diff --git a/include/uapi/linux/rtnetlink.h b/include/uapi/linux/rtnetlink.h
> index 1418a8362bb7..e5a104f5ce35 100644
> --- a/include/uapi/linux/rtnetlink.h
> +++ b/include/uapi/linux/rtnetlink.h
> @@ -309,6 +309,7 @@ enum rt_scope_t {
> #define RTM_F_PREFIX 0x800 /* Prefix addresses */
> #define RTM_F_LOOKUP_TABLE 0x1000 /* set rtm_table to FIB lookup result */
> #define RTM_F_FIB_MATCH 0x2000 /* return full fib lookup match */
> +#define RTM_F_IN_HW 0x4000 /* route is in hardware */
>
> /* Reserved table identifiers */
>
> diff --git a/net/ipv4/fib_lookup.h b/net/ipv4/fib_lookup.h
> index b34594a9965f..65a69a863499 100644
> --- a/net/ipv4/fib_lookup.h
> +++ b/net/ipv4/fib_lookup.h
> @@ -16,6 +16,8 @@ struct fib_alias {
> u8 fa_slen;
> u32 tb_id;
> s16 fa_default;
> + u8 in_hw:1,
> + unused:7;
> struct rcu_head rcu;
> };
>
> @@ -28,6 +30,8 @@ struct fib_rt_info {
> int dst_len;
> u8 tos;
> u8 type;
> + u8 in_hw:1,
> + unused:7;
> };
>
> /* Dont write on fa_state unless needed, to keep it shared on all cpus */
> diff --git a/net/ipv4/fib_semantics.c b/net/ipv4/fib_semantics.c
> index 3c9d47804d93..94f201d44844 100644
> --- a/net/ipv4/fib_semantics.c
> +++ b/net/ipv4/fib_semantics.c
> @@ -519,6 +519,7 @@ void rtmsg_fib(int event, __be32 key, struct fib_alias *fa,
> fri.dst_len = dst_len;
> fri.tos = fa->fa_tos;
> fri.type = fa->fa_type;
> + fri.in_hw = fa->in_hw;
> err = fib_dump_info(skb, info->portid, seq, event, &fri, nlm_flags);
> if (err < 0) {
> /* -EMSGSIZE implies BUG in fib_nlmsg_size() */
> @@ -1801,6 +1802,9 @@ int fib_dump_info(struct sk_buff *skb, u32 portid, u32 seq, int event,
> goto nla_put_failure;
> }
>
> + if (fri->in_hw)
> + rtm->rtm_flags |= RTM_F_IN_HW;
> +
> nlmsg_end(skb, nlh);
> return 0;
>
> diff --git a/net/ipv4/fib_trie.c b/net/ipv4/fib_trie.c
> index 646542de83ca..e3486bde6c5a 100644
> --- a/net/ipv4/fib_trie.c
> +++ b/net/ipv4/fib_trie.c
> @@ -1028,6 +1028,74 @@ static struct fib_alias *fib_find_alias(struct hlist_head *fah, u8 slen,
> return NULL;
> }
>
> +static struct fib_alias *
> +fib_find_matching_alias(struct net *net, u32 dst, int dst_len,
> + const struct fib_info *fi, u8 tos, u8 type, u32 tb_id)
> +{
> + u8 slen = KEYLENGTH - dst_len;
> + struct key_vector *l, *tp;
> + struct fib_table *tb;
> + struct fib_alias *fa;
> + struct trie *t;
> +
> + tb = fib_get_table(net, tb_id);
> + if (!tb)
> + return NULL;
> +
> + t = (struct trie *)tb->tb_data;
> + l = fib_find_node(t, &tp, dst);
> + if (!l)
> + return NULL;
> +
> + hlist_for_each_entry_rcu(fa, &l->leaf, fa_list) {
> + if (fa->fa_slen == slen && fa->tb_id == tb_id &&
> + fa->fa_tos == tos && fa->fa_info == fi &&
> + fa->fa_type == type)
> + return fa;
> + }
> +
> + return NULL;
> +}
> +
> +void fib_alias_in_hw_set(struct net *net, u32 dst, int dst_len,
> + const struct fib_info *fi, u8 tos, u8 type, u32 tb_id)
> +{
> + struct fib_alias *fa_match;
> +
> + rcu_read_lock();
> +
> + fa_match = fib_find_matching_alias(net, dst, dst_len, fi, tos, type,
> + tb_id);
> + if (!fa_match)
> + goto out;
> +
> + fa_match->in_hw = 1;
> +
> +out:
> + rcu_read_unlock();
> +}
> +EXPORT_SYMBOL_GPL(fib_alias_in_hw_set);
> +
> +void fib_alias_in_hw_clear(struct net *net, u32 dst, int dst_len,
> + const struct fib_info *fi, u8 tos, u8 type,
> + u32 tb_id)
> +{
> + struct fib_alias *fa_match;
> +
> + rcu_read_lock();
> +
> + fa_match = fib_find_matching_alias(net, dst, dst_len, fi, tos, type,
> + tb_id);
> + if (!fa_match)
> + goto out;
> +
> + fa_match->in_hw = 0;
> +
> +out:
> + rcu_read_unlock();
> +}
> +EXPORT_SYMBOL_GPL(fib_alias_in_hw_clear);
> +
> static void trie_rebalance(struct trie *t, struct key_vector *tn)
> {
> while (!IS_TRIE(tn))
> @@ -1236,6 +1304,7 @@ int fib_table_insert(struct net *net, struct fib_table *tb,
> new_fa->fa_slen = fa->fa_slen;
> new_fa->tb_id = tb->tb_id;
> new_fa->fa_default = -1;
> + new_fa->in_hw = 0;
>
> hlist_replace_rcu(&fa->fa_list, &new_fa->fa_list);
>
> @@ -1294,6 +1363,7 @@ int fib_table_insert(struct net *net, struct fib_table *tb,
> new_fa->fa_slen = slen;
> new_fa->tb_id = tb->tb_id;
> new_fa->fa_default = -1;
> + new_fa->in_hw = 0;
>
> /* Insert new entry to the list. */
> err = fib_insert_alias(t, tp, l, new_fa, fa, key);
> @@ -2218,6 +2288,7 @@ static int fn_trie_dump_leaf(struct key_vector *l, struct fib_table *tb,
> fri.dst_len = KEYLENGTH - fa->fa_slen;
> fri.tos = fa->fa_tos;
> fri.type = fa->fa_type;
> + fri.in_hw = fa->in_hw;
> err = fib_dump_info(skb,
> NETLINK_CB(cb->skb).portid,
> cb->nlh->nlmsg_seq,
> --
> 2.21.0
>
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