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Message-ID: <18594f40-f86f-4a28-a97a-22d8d8b614b6@intel.com>
Date: Fri, 29 Aug 2025 17:46:28 +0200
From: Alexander Lobakin <aleksander.lobakin@...el.com>
To: Yue Haibing <yuehaibing@...wei.com>
CC: <davem@...emloft.net>, <dsahern@...nel.org>, <edumazet@...gle.com>,
<kuba@...nel.org>, <pabeni@...hat.com>, <horms@...nel.org>,
<netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 net-next] ipv6: sit: Add ipip6_tunnel_dst_find() for
cleanup
From: Yue Haibing <yuehaibing@...wei.com>
Date: Fri, 29 Aug 2025 18:09:46 +0800
> Extract the dst lookup logic from ipip6_tunnel_xmit() into new helper
> ipip6_tunnel_dst_find() to reduce code duplication and enhance readability.
> No functional change intended.
Reviewed-by: Alexander Lobakin <aleksander.lobakin@...el.com>
>
> On a x86_64, with allmodconfig object size is also reduced:
>
> ./scripts/bloat-o-meter net/ipv6/sit.o net/ipv6/sit-new.o
> add/remove: 5/3 grow/shrink: 3/4 up/down: 1841/-2275 (-434)
> Function old new delta
> ipip6_tunnel_dst_find - 1697 +1697
> __pfx_ipip6_tunnel_dst_find - 64 +64
> __UNIQUE_ID_modinfo2094 - 43 +43
> ipip6_tunnel_xmit.isra.cold 79 88 +9
> __UNIQUE_ID_modinfo2096 12 20 +8
> __UNIQUE_ID___addressable_init_module2092 - 8 +8
> __UNIQUE_ID___addressable_cleanup_module2093 - 8 +8
> __func__ 55 59 +4
> __UNIQUE_ID_modinfo2097 20 18 -2
> __UNIQUE_ID___addressable_init_module2093 8 - -8
> __UNIQUE_ID___addressable_cleanup_module2094 8 - -8
> __UNIQUE_ID_modinfo2098 18 - -18
> __UNIQUE_ID_modinfo2095 43 12 -31
> descriptor 112 56 -56
> ipip6_tunnel_xmit.isra 9910 7758 -2152
> Total: Before=72537, After=72103, chg -0.60%
>
> Signed-off-by: Yue Haibing <yuehaibing@...wei.com>
> ---
> v2: add newlines before return in ipip6_tunnel_dst_find()
> add bloat-o-meter info in commit log
> ---
> net/ipv6/sit.c | 95 ++++++++++++++++++++++++--------------------------
> 1 file changed, 45 insertions(+), 50 deletions(-)
>
> diff --git a/net/ipv6/sit.c b/net/ipv6/sit.c
> index 12496ba1b7d4..60bd7f01fa09 100644
> --- a/net/ipv6/sit.c
> +++ b/net/ipv6/sit.c
> @@ -848,6 +848,49 @@ static inline __be32 try_6rd(struct ip_tunnel *tunnel,
> return dst;
> }
>
> +static bool ipip6_tunnel_dst_find(struct sk_buff *skb, __be32 *dst,
> + bool is_isatap)
> +{
> + const struct ipv6hdr *iph6 = ipv6_hdr(skb);
> + struct neighbour *neigh = NULL;
> + const struct in6_addr *addr6;
> + bool found = false;
> + int addr_type;
> +
> + if (skb_dst(skb))
> + neigh = dst_neigh_lookup(skb_dst(skb), &iph6->daddr);
> +
> + if (!neigh) {
> + net_dbg_ratelimited("nexthop == NULL\n");
> + return false;
> + }
> +
> + addr6 = (const struct in6_addr *)&neigh->primary_key;
> + addr_type = ipv6_addr_type(addr6);
> +
> + if (is_isatap) {
> + if ((addr_type & IPV6_ADDR_UNICAST) &&
> + ipv6_addr_is_isatap(addr6)) {
> + *dst = addr6->s6_addr32[3];
> + found = true;
> + }
> + } else {
> + if (addr_type == IPV6_ADDR_ANY) {
> + addr6 = &ipv6_hdr(skb)->daddr;
> + addr_type = ipv6_addr_type(addr6);
> + }
> +
> + if ((addr_type & IPV6_ADDR_COMPATv4) != 0) {
> + *dst = addr6->s6_addr32[3];
> + found = true;
> + }
> + }
> +
> + neigh_release(neigh);
> +
> + return found;
> +}
> +
> /*
> * This function assumes it is being called from dev_queue_xmit()
> * and that skb is filled properly by that function.
> @@ -867,8 +910,6 @@ static netdev_tx_t ipip6_tunnel_xmit(struct sk_buff *skb,
> __be32 dst = tiph->daddr;
> struct flowi4 fl4;
> int mtu;
> - const struct in6_addr *addr6;
> - int addr_type;
> u8 ttl;
> u8 protocol = IPPROTO_IPV6;
> int t_hlen = tunnel->hlen + sizeof(struct iphdr);
> @@ -878,28 +919,7 @@ static netdev_tx_t ipip6_tunnel_xmit(struct sk_buff *skb,
>
> /* ISATAP (RFC4214) - must come before 6to4 */
> if (dev->priv_flags & IFF_ISATAP) {
> - struct neighbour *neigh = NULL;
> - bool do_tx_error = false;
> -
> - if (skb_dst(skb))
> - neigh = dst_neigh_lookup(skb_dst(skb), &iph6->daddr);
> -
> - if (!neigh) {
> - net_dbg_ratelimited("nexthop == NULL\n");
> - goto tx_error;
> - }
> -
> - addr6 = (const struct in6_addr *)&neigh->primary_key;
> - addr_type = ipv6_addr_type(addr6);
> -
> - if ((addr_type & IPV6_ADDR_UNICAST) &&
> - ipv6_addr_is_isatap(addr6))
> - dst = addr6->s6_addr32[3];
> - else
> - do_tx_error = true;
> -
> - neigh_release(neigh);
> - if (do_tx_error)
> + if (!ipip6_tunnel_dst_find(skb, &dst, true))
> goto tx_error;
> }
Ooops, sorry that I didn't notice that before.
You can flatten the conditions now:
if ((dev->priv_flags & IFF_ISATAP) &&
!ipip6_tunnel_dst_find(skb, &dst, true))
goto tx_error;
>
> @@ -907,32 +927,7 @@ static netdev_tx_t ipip6_tunnel_xmit(struct sk_buff *skb,
> dst = try_6rd(tunnel, &iph6->daddr);
>
> if (!dst) {
> - struct neighbour *neigh = NULL;
> - bool do_tx_error = false;
> -
> - if (skb_dst(skb))
> - neigh = dst_neigh_lookup(skb_dst(skb), &iph6->daddr);
> -
> - if (!neigh) {
> - net_dbg_ratelimited("nexthop == NULL\n");
> - goto tx_error;
> - }
> -
> - addr6 = (const struct in6_addr *)&neigh->primary_key;
> - addr_type = ipv6_addr_type(addr6);
> -
> - if (addr_type == IPV6_ADDR_ANY) {
> - addr6 = &ipv6_hdr(skb)->daddr;
> - addr_type = ipv6_addr_type(addr6);
> - }
> -
> - if ((addr_type & IPV6_ADDR_COMPATv4) != 0)
> - dst = addr6->s6_addr32[3];
> - else
> - do_tx_error = true;
> -
> - neigh_release(neigh);
> - if (do_tx_error)
> + if (!ipip6_tunnel_dst_find(skb, &dst, false))
> goto tx_error;
> }
Same here:
if (!dst && !ipip6_tunnel_dst_find(skb, &dst, false))
goto tx_error;
Thanks,
Olek
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