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Message-ID: <55CB9C1F.7000702@brocade.com>
Date: Wed, 12 Aug 2015 20:18:55 +0100
From: Robert Shearman <rshearma@...cade.com>
To: Roopa Prabhu <roopa@...ulusnetworks.com>, <davem@...emloft.net>
CC: <ebiederm@...ssion.com>, <netdev@...r.kernel.org>
Subject: Re: [PATCH net-next 3/3] mpls: add multipath route support
On 11/08/15 22:45, Roopa Prabhu wrote:
> From: Roopa Prabhu <roopa@...ulusnetworks.com>
>
> Adds support for MPLS multipath routes.
> supports parse/fill of RTA_MULTIPATH netlink attribute
> for multipath routes similar to ipv4 fib. Mostly based on
> multipath handling in ipv4 fib code.
>
> The multipath route nexthop selection algorithm is the same
> code as in ipv4 fib.
>
> This patch also adds new functions to parse multipath attributes
> from route config into mpls_nhlfe.
>
> note that it also simplifies mpls_route_update. Removes handling
> route updates based on dev argument. The reason for
> doing that is, the function was not being used for route updates
> based on dev and if we do need to support route updates based
> on dev in the future it will have to be done differently.
>
> Signed-off-by: Roopa Prabhu <roopa@...ulusnetworks.com>
> ---
> net/mpls/af_mpls.c | 378 +++++++++++++++++++++++++++++++++++++++++----------
> net/mpls/internal.h | 19 +++
> 2 files changed, 323 insertions(+), 74 deletions(-)
>
> diff --git a/net/mpls/af_mpls.c b/net/mpls/af_mpls.c
> index eb089ef..de5ae29 100644
> --- a/net/mpls/af_mpls.c
> +++ b/net/mpls/af_mpls.c
> @@ -19,10 +19,12 @@
> #include <net/ipv6.h>
> #include <net/addrconf.h>
> #endif
> +#include <net/nexthop.h>
> #include "internal.h"
>
> static int zero = 0;
> static int label_limit = (1 << 20) - 1;
> +static DEFINE_SPINLOCK(mpls_multipath_lock);
>
> static void rtmsg_lfib(int event, u32 label, struct mpls_route *rt,
> struct nlmsghdr *nlh, struct net *net, u32 portid,
> @@ -51,10 +53,10 @@ bool mpls_output_possible(const struct net_device *dev)
> }
> EXPORT_SYMBOL_GPL(mpls_output_possible);
>
> -static unsigned int mpls_rt_header_size(const struct mpls_route *rt)
> +static unsigned int mpls_nhlfe_header_size(const struct mpls_nhlfe *nhlfe)
> {
> /* The size of the layer 2.5 labels to be added for this route */
> - return rt->rt_nh->nh_labels * sizeof(struct mpls_shim_hdr);
> + return nhlfe->nh_labels * sizeof(struct mpls_shim_hdr);
> }
>
> unsigned int mpls_dev_mtu(const struct net_device *dev)
> @@ -76,7 +78,52 @@ bool mpls_pkt_too_big(const struct sk_buff *skb, unsigned int mtu)
> }
> EXPORT_SYMBOL_GPL(mpls_pkt_too_big);
>
> -static bool mpls_egress(struct mpls_route *rt, struct sk_buff *skb,
> +/* This is a cut/copy/modify from fib_select_multipath */
> +static void mpls_select_multipath(struct mpls_route *rt, int *nhidx)
> +{
> + int w;
> +
> + spin_lock_bh(&mpls_multipath_lock);
> + if (rt->rt_power <= 0) {
> + int power = 0;
> +
> + change_nexthops(rt) {
> + power += nhlfe->nh_weight;
> + nhlfe->nh_power = nhlfe->nh_weight;
> + } endfor_nexthops(rt);
> + rt->rt_power = power;
> + if (power <= 0) {
> + spin_unlock_bh(&mpls_multipath_lock);
> + /* Race condition: route has just become dead. */
> + *nhidx = 0;
> + return;
> + }
> + }
> +
> + /* w should be random number [0..rt->rt_power-1],
> + * it is pretty bad approximation.
> + */
> + w = jiffies % rt->rt_power;
> +
> + change_nexthops(rt) {
> + if (nhlfe->nh_power) {
> + w -= nhlfe->nh_power;
> + if (w <= 0) {
> + nhlfe->nh_power--;
> + rt->rt_power--;
> + *nhidx = nhsel;
> + spin_unlock_bh(&mpls_multipath_lock);
> + return;
> + }
> + }
> + } endfor_nexthops(rt);
> +
> + /* Race condition: route has just become dead. */
> + *nhidx = 0;
> + spin_unlock_bh(&mpls_multipath_lock);
> +}
If we were to do flow-based hashing then this would also avoid the
locking required here.
> +
> +static bool mpls_egress(struct mpls_nhlfe *nhlfe, struct sk_buff *skb,
> struct mpls_entry_decoded dec)
> {
> enum mpls_payload_type payload_type;
> @@ -95,7 +142,7 @@ static bool mpls_egress(struct mpls_route *rt, struct sk_buff *skb,
> if (!pskb_may_pull(skb, 12))
> return false;
>
> - payload_type = rt->rt_nh->nh_payload_type;
> + payload_type = nhlfe->nh_payload_type;
> if (payload_type == MPT_UNSPEC)
> payload_type = ip_hdr(skb)->version;
>
> @@ -130,6 +177,7 @@ static int mpls_forward(struct sk_buff *skb, struct net_device *dev,
> struct net *net = dev_net(dev);
> struct mpls_shim_hdr *hdr;
> struct mpls_route *rt;
> + struct mpls_nhlfe *nhlfe;
> struct mpls_entry_decoded dec;
> struct net_device *out_dev;
> struct mpls_dev *mdev;
> @@ -137,6 +185,7 @@ static int mpls_forward(struct sk_buff *skb, struct net_device *dev,
> unsigned int new_header_size;
> unsigned int mtu;
> int err;
> + int nhidx;
>
> /* Careful this entire function runs inside of an rcu critical section */
>
> @@ -167,9 +216,12 @@ static int mpls_forward(struct sk_buff *skb, struct net_device *dev,
> if (!rt)
> goto drop;
>
> + mpls_select_multipath(rt, &nhidx);
> + nhlfe = &rt->rt_nh[nhidx];
How about just returning the nexthop from mpls_select_multipath rather
than going via nhidx?
> +
> /* Find the output device */
> - out_dev = rcu_dereference(rt->rt_nh->nh_dev);
> - if (!mpls_output_possible(out_dev))
> + out_dev = rcu_dereference(nhlfe->nh_dev);
> + if (!out_dev || !mpls_output_possible(out_dev))
> goto drop;
>
> if (skb_warn_if_lro(skb))
...
> @@ -796,6 +954,48 @@ int nla_get_labels(const struct nlattr *nla,
> }
> EXPORT_SYMBOL_GPL(nla_get_labels);
>
> +int nla_get_via(const struct nlattr *nla, u8 *via_alen,
> + u8 *via_table, u8 via_addr[])
This isn't used by any other source files so couldn't this be made static?
> +{
> + struct rtvia *via = nla_data(nla);
> + int err = -EINVAL;
> + u8 alen;
Should this be an int to avoid false negatives below for large values of
nla_len?
> +
> + if (nla_len(nla) < offsetof(struct rtvia, rtvia_addr))
> + goto errout;
> + alen = nla_len(nla) -
> + offsetof(struct rtvia, rtvia_addr);
> + if (alen > MAX_VIA_ALEN)
> + goto errout;
> +
> + /* Validate the address family */
> + switch (via->rtvia_family) {
> + case AF_PACKET:
> + *via_table = NEIGH_LINK_TABLE;
> + break;
> + case AF_INET:
> + *via_table = NEIGH_ARP_TABLE;
> + if (alen != 4)
> + goto errout;
> + break;
> + case AF_INET6:
> + *via_table = NEIGH_ND_TABLE;
> + if (alen != 16)
> + goto errout;
> + break;
> + default:
> + /* Unsupported address family */
> + goto errout;
> + }
> +
> + memcpy(via_addr, via->rtvia_addr, alen);
> + *via_alen = alen;
> + err = 0;
> +
> +errout:
> + return err;
> +}
> +
> static int rtm_to_route_config(struct sk_buff *skb, struct nlmsghdr *nlh,
> struct mpls_route_config *cfg)
> {
> @@ -872,35 +1072,15 @@ static int rtm_to_route_config(struct sk_buff *skb, struct nlmsghdr *nlh,
> }
> case RTA_VIA:
> {
> - struct rtvia *via = nla_data(nla);
> - if (nla_len(nla) < offsetof(struct rtvia, rtvia_addr))
> - goto errout;
> - cfg->rc_via_alen = nla_len(nla) -
> - offsetof(struct rtvia, rtvia_addr);
> - if (cfg->rc_via_alen > MAX_VIA_ALEN)
> - goto errout;
> -
> - /* Validate the address family */
> - switch(via->rtvia_family) {
> - case AF_PACKET:
> - cfg->rc_via_table = NEIGH_LINK_TABLE;
> - break;
> - case AF_INET:
> - cfg->rc_via_table = NEIGH_ARP_TABLE;
> - if (cfg->rc_via_alen != 4)
> - goto errout;
> - break;
> - case AF_INET6:
> - cfg->rc_via_table = NEIGH_ND_TABLE;
> - if (cfg->rc_via_alen != 16)
> - goto errout;
> - break;
> - default:
> - /* Unsupported address family */
> + if (nla_get_via(nla, &cfg->rc_via_alen,
> + &cfg->rc_via_table, cfg->rc_via))
> goto errout;
> - }
> -
> - memcpy(cfg->rc_via, via->rtvia_addr, cfg->rc_via_alen);
> + break;
> + }
> + case RTA_MULTIPATH:
> + {
> + cfg->rc_mp = nla_data(nla);
> + cfg->rc_mp_len = nla_len(nla);
> break;
> }
Nit: these scope brackets can be removed here and now above for the
RTA_VIA case.
> default:
Thanks,
Rob
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