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Subject[PATCH 5.3 026/344] ipv4: Revert removal of rt_uses_gateway
Date
From: David Ahern <dsahern@gmail.com>

[ Upstream commit 77d5bc7e6a6cf8bbeca31aab7f0c5449a5eee762 ]

Julian noted that rt_uses_gateway has a more subtle use than 'is gateway
set':
https://lore.kernel.org/netdev/alpine.LFD.2.21.1909151104060.2546@ja.home.ssi.bg/

Revert that part of the commit referenced in the Fixes tag.

Currently, there are no u8 holes in 'struct rtable'. There is a 4-byte hole
in the second cacheline which contains the gateway declaration. So move
rt_gw_family down to the gateway declarations since they are always used
together, and then re-use that u8 for rt_uses_gateway. End result is that
rtable size is unchanged.

Fixes: 1550c171935d ("ipv4: Prepare rtable for IPv6 gateway")
Reported-by: Julian Anastasov <ja@ssi.bg>
Signed-off-by: David Ahern <dsahern@gmail.com>
Reviewed-by: Julian Anastasov <ja@ssi.bg>
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/infiniband/core/addr.c | 2 +-
include/net/route.h | 3 ++-
net/ipv4/inet_connection_sock.c | 4 ++--
net/ipv4/ip_forward.c | 2 +-
net/ipv4/ip_output.c | 2 +-
net/ipv4/route.c | 36 +++++++++++++++++++++---------------
net/ipv4/xfrm4_policy.c | 1 +
7 files changed, 29 insertions(+), 21 deletions(-)

--- a/drivers/infiniband/core/addr.c
+++ b/drivers/infiniband/core/addr.c
@@ -352,7 +352,7 @@ static bool has_gateway(const struct dst

if (family == AF_INET) {
rt = container_of(dst, struct rtable, dst);
- return rt->rt_gw_family == AF_INET;
+ return rt->rt_uses_gateway;
}

rt6 = container_of(dst, struct rt6_info, dst);
--- a/include/net/route.h
+++ b/include/net/route.h
@@ -53,10 +53,11 @@ struct rtable {
unsigned int rt_flags;
__u16 rt_type;
__u8 rt_is_input;
- u8 rt_gw_family;
+ __u8 rt_uses_gateway;

int rt_iif;

+ u8 rt_gw_family;
/* Info on neighbour */
union {
__be32 rt_gw4;
--- a/net/ipv4/inet_connection_sock.c
+++ b/net/ipv4/inet_connection_sock.c
@@ -560,7 +560,7 @@ struct dst_entry *inet_csk_route_req(con
rt = ip_route_output_flow(net, fl4, sk);
if (IS_ERR(rt))
goto no_route;
- if (opt && opt->opt.is_strictroute && rt->rt_gw_family)
+ if (opt && opt->opt.is_strictroute && rt->rt_uses_gateway)
goto route_err;
rcu_read_unlock();
return &rt->dst;
@@ -598,7 +598,7 @@ struct dst_entry *inet_csk_route_child_s
rt = ip_route_output_flow(net, fl4, sk);
if (IS_ERR(rt))
goto no_route;
- if (opt && opt->opt.is_strictroute && rt->rt_gw_family)
+ if (opt && opt->opt.is_strictroute && rt->rt_uses_gateway)
goto route_err;
return &rt->dst;

--- a/net/ipv4/ip_forward.c
+++ b/net/ipv4/ip_forward.c
@@ -123,7 +123,7 @@ int ip_forward(struct sk_buff *skb)

rt = skb_rtable(skb);

- if (opt->is_strictroute && rt->rt_gw_family)
+ if (opt->is_strictroute && rt->rt_uses_gateway)
goto sr_failed;

IPCB(skb)->flags |= IPSKB_FORWARDED;
--- a/net/ipv4/ip_output.c
+++ b/net/ipv4/ip_output.c
@@ -499,7 +499,7 @@ int __ip_queue_xmit(struct sock *sk, str
skb_dst_set_noref(skb, &rt->dst);

packet_routed:
- if (inet_opt && inet_opt->opt.is_strictroute && rt->rt_gw_family)
+ if (inet_opt && inet_opt->opt.is_strictroute && rt->rt_uses_gateway)
goto no_route;

/* OK, we know where to send it, allocate and build IP header. */
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -635,6 +635,7 @@ static void fill_route_from_fnhe(struct

if (fnhe->fnhe_gw) {
rt->rt_flags |= RTCF_REDIRECTED;
+ rt->rt_uses_gateway = 1;
rt->rt_gw_family = AF_INET;
rt->rt_gw4 = fnhe->fnhe_gw;
}
@@ -1313,7 +1314,7 @@ static unsigned int ipv4_mtu(const struc
mtu = READ_ONCE(dst->dev->mtu);

if (unlikely(ip_mtu_locked(dst))) {
- if (rt->rt_gw_family && mtu > 576)
+ if (rt->rt_uses_gateway && mtu > 576)
mtu = 576;
}

@@ -1569,6 +1570,7 @@ static void rt_set_nexthop(struct rtable
struct fib_nh_common *nhc = FIB_RES_NHC(*res);

if (nhc->nhc_gw_family && nhc->nhc_scope == RT_SCOPE_LINK) {
+ rt->rt_uses_gateway = 1;
rt->rt_gw_family = nhc->nhc_gw_family;
/* only INET and INET6 are supported */
if (likely(nhc->nhc_gw_family == AF_INET))
@@ -1634,6 +1636,7 @@ struct rtable *rt_dst_alloc(struct net_d
rt->rt_iif = 0;
rt->rt_pmtu = 0;
rt->rt_mtu_locked = 0;
+ rt->rt_uses_gateway = 0;
rt->rt_gw_family = 0;
rt->rt_gw4 = 0;
INIT_LIST_HEAD(&rt->rt_uncached);
@@ -2694,6 +2697,7 @@ struct dst_entry *ipv4_blackhole_route(s
rt->rt_genid = rt_genid_ipv4(net);
rt->rt_flags = ort->rt_flags;
rt->rt_type = ort->rt_type;
+ rt->rt_uses_gateway = ort->rt_uses_gateway;
rt->rt_gw_family = ort->rt_gw_family;
if (rt->rt_gw_family == AF_INET)
rt->rt_gw4 = ort->rt_gw4;
@@ -2778,21 +2782,23 @@ static int rt_fill_info(struct net *net,
if (nla_put_in_addr(skb, RTA_PREFSRC, fl4->saddr))
goto nla_put_failure;
}
- if (rt->rt_gw_family == AF_INET &&
- nla_put_in_addr(skb, RTA_GATEWAY, rt->rt_gw4)) {
- goto nla_put_failure;
- } else if (rt->rt_gw_family == AF_INET6) {
- int alen = sizeof(struct in6_addr);
- struct nlattr *nla;
- struct rtvia *via;
-
- nla = nla_reserve(skb, RTA_VIA, alen + 2);
- if (!nla)
+ if (rt->rt_uses_gateway) {
+ if (rt->rt_gw_family == AF_INET &&
+ nla_put_in_addr(skb, RTA_GATEWAY, rt->rt_gw4)) {
goto nla_put_failure;
-
- via = nla_data(nla);
- via->rtvia_family = AF_INET6;
- memcpy(via->rtvia_addr, &rt->rt_gw6, alen);
+ } else if (rt->rt_gw_family == AF_INET6) {
+ int alen = sizeof(struct in6_addr);
+ struct nlattr *nla;
+ struct rtvia *via;
+
+ nla = nla_reserve(skb, RTA_VIA, alen + 2);
+ if (!nla)
+ goto nla_put_failure;
+
+ via = nla_data(nla);
+ via->rtvia_family = AF_INET6;
+ memcpy(via->rtvia_addr, &rt->rt_gw6, alen);
+ }
}

expires = rt->dst.expires;
--- a/net/ipv4/xfrm4_policy.c
+++ b/net/ipv4/xfrm4_policy.c
@@ -85,6 +85,7 @@ static int xfrm4_fill_dst(struct xfrm_ds
xdst->u.rt.rt_flags = rt->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST |
RTCF_LOCAL);
xdst->u.rt.rt_type = rt->rt_type;
+ xdst->u.rt.rt_uses_gateway = rt->rt_uses_gateway;
xdst->u.rt.rt_gw_family = rt->rt_gw_family;
if (rt->rt_gw_family == AF_INET)
xdst->u.rt.rt_gw4 = rt->rt_gw4;

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