[PATCH net-next] ipv6: sit: Add ipip6_tunnel_dst_find() for cleanup

[PATCH net-next] ipv6: sit: Add ipip6_tunnel_dst_find() for cleanup

[Yue Haibing]

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.

Signed-off-by: Yue Haibing <yuehaibing@huawei.com>
---
 net/ipv6/sit.c | 93 +++++++++++++++++++++++---------------------------
 1 file changed, 43 insertions(+), 50 deletions(-)

diff --git a/net/ipv6/sit.c b/net/ipv6/sit.c
index 12496ba1b7d4..bcd261ff985b 100644
--- a/net/ipv6/sit.c
+++ b/net/ipv6/sit.c
@@ -848,6 +848,47 @@ 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 found;
+	}
+
+	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 +908,6 @@ 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 +917,7 @@ 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;
 	}
 
@@ -907,32 +925,7 @@ 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;
 	}
 
-- 
2.34.1

Re: [PATCH net-next] ipv6: sit: Add ipip6_tunnel_dst_find() for cleanup

[Alexander Lobakin]

From: Yue Haibing <yuehaibing@huawei.com>
Date: Wed, 27 Aug 2025 12:00:27 +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.

...but bloat-o-meter stats would be nice to see here. I'm curious
whether the object code got any changes or the compilers still just
inline this function to both call sites.

> 
> Signed-off-by: Yue Haibing <yuehaibing@huawei.com>
> ---
>  net/ipv6/sit.c | 93 +++++++++++++++++++++++---------------------------
>  1 file changed, 43 insertions(+), 50 deletions(-)
> 
> diff --git a/net/ipv6/sit.c b/net/ipv6/sit.c
> index 12496ba1b7d4..bcd261ff985b 100644
> --- a/net/ipv6/sit.c
> +++ b/net/ipv6/sit.c
> @@ -848,6 +848,47 @@ 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 found;

Return false here right away.

> +	}
> +
> +	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;

I'd put 2 additional newlines here:

	}

	neigh_release(neigh);

	return found;
}

for readability purposes and also a NL before the final `return` is
usually mandatory.

Thanks,
Olek

Re: [PATCH net-next] ipv6: sit: Add ipip6_tunnel_dst_find() for cleanup

[Yue Haibing]

On 2025/8/27 22:45, Alexander Lobakin wrote:
> From: Yue Haibing <yuehaibing@huawei.com>
> Date: Wed, 27 Aug 2025 12:00:27 +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.
> 
> ...but bloat-o-meter stats would be nice to see here. I'm curious
> whether the object code got any changes or the compilers still just
> inline this function to both call sites.

On a x86_64, with allmodconfig:
before:
   text    data     bss     dec     hex filename
  96973   14687     256  111916   1b52c net/ipv6/sit.o

after:
   text    data     bss     dec     hex filename
  96699   14599     256  111554   1b3c2 net/ipv6/sit.o

I will add this in v2.

> 
>>
>> Signed-off-by: Yue Haibing <yuehaibing@huawei.com>
>> ---
>>  net/ipv6/sit.c | 93 +++++++++++++++++++++++---------------------------
>>  1 file changed, 43 insertions(+), 50 deletions(-)
>>
>> diff --git a/net/ipv6/sit.c b/net/ipv6/sit.c
>> index 12496ba1b7d4..bcd261ff985b 100644
>> --- a/net/ipv6/sit.c
>> +++ b/net/ipv6/sit.c
>> @@ -848,6 +848,47 @@ 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 found;
> 
> Return false here right away.
> 
>> +	}
>> +
>> +	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;
> 
> I'd put 2 additional newlines here:
> 
> 	}
> 
> 	neigh_release(neigh);
> 
> 	return found;
> }
> 
> for readability purposes and also a NL before the final `return` is
> usually mandatory.

OK， thanks.
> 
> Thanks,
> Olek
> 

Re: [PATCH net-next] ipv6: sit: Add ipip6_tunnel_dst_find() for cleanup

[Yue Haibing]

On 2025/8/28 14:13, Yue Haibing wrote:
> On 2025/8/27 22:45, Alexander Lobakin wrote:
>> From: Yue Haibing <yuehaibing@huawei.com>
>> Date: Wed, 27 Aug 2025 12:00:27 +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.
>>
>> ...but bloat-o-meter stats would be nice to see here. I'm curious
>> whether the object code got any changes or the compilers still just
>> inline this function to both call sites.

On a x86_64, with allmodconfig:

./scripts/bloat-o-meter -c net/ipv6/sit.o net/ipv6/sit-after.o
add/remove: 2/0 grow/shrink: 1/1 up/down: 1770/-2152 (-382)
Function                                     old     new   delta
ipip6_tunnel_dst_find                          -    1697   +1697
__pfx_ipip6_tunnel_dst_find                    -      64     +64
ipip6_tunnel_xmit.isra.cold                   79      88      +9
ipip6_tunnel_xmit.isra                      9910    7758   -2152
Total: Before=70060, After=69678, chg -0.55%
add/remove: 2/2 grow/shrink: 0/1 up/down: 16/-72 (-56)
Data                                         old     new   delta
__UNIQUE_ID___addressable_init_module2092       -       8      +8
__UNIQUE_ID___addressable_cleanup_module2093       -       8      +8
__UNIQUE_ID___addressable_init_module2093       8       -      -8
__UNIQUE_ID___addressable_cleanup_module2094       8       -      -8
descriptor                                   112      56     -56
Total: Before=752, After=696, chg -7.45%
add/remove: 1/1 grow/shrink: 2/2 up/down: 55/-51 (4)
RO Data                                      old     new   delta
__UNIQUE_ID_modinfo2094                        -      43     +43
__UNIQUE_ID_modinfo2096                       12      20      +8
__func__                                      55      59      +4
__UNIQUE_ID_modinfo2097                       20      18      -2
__UNIQUE_ID_modinfo2098                       18       -     -18
__UNIQUE_ID_modinfo2095                       43      12     -31
Total: Before=1725, After=1729, chg +0.23%


> 
> On a x86_64, with allmodconfig:
> before:
>    text    data     bss     dec     hex filename
>   96973   14687     256  111916   1b52c net/ipv6/sit.o
> 
> after:
>    text    data     bss     dec     hex filename
>   96699   14599     256  111554   1b3c2 net/ipv6/sit.o
> 
> I will add this in v2.
> 
>>
>>>
>>> Signed-off-by: Yue Haibing <yuehaibing@huawei.com>
>>> ---
>>>  net/ipv6/sit.c | 93 +++++++++++++++++++++++---------------------------
>>>  1 file changed, 43 insertions(+), 50 deletions(-)
>>>
>>> diff --git a/net/ipv6/sit.c b/net/ipv6/sit.c
>>> index 12496ba1b7d4..bcd261ff985b 100644
>>> --- a/net/ipv6/sit.c
>>> +++ b/net/ipv6/sit.c
>>> @@ -848,6 +848,47 @@ 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 found;
>>
>> Return false here right away.
>>
>>> +	}
>>> +
>>> +	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;
>>
>> I'd put 2 additional newlines here:
>>
>> 	}
>>
>> 	neigh_release(neigh);
>>
>> 	return found;
>> }
>>
>> for readability purposes and also a NL before the final `return` is
>> usually mandatory.
> 
> OK， thanks.
>>
>> Thanks,
>> Olek
>>
> 
> 

Re: [PATCH net-next] ipv6: sit: Add ipip6_tunnel_dst_find() for cleanup

[Alexander Lobakin]

From: Yue Haibing <yuehaibing@huawei.com>
Date: Thu, 28 Aug 2025 14:44:07 +0800

> On 2025/8/28 14:13, Yue Haibing wrote:
>> On 2025/8/27 22:45, Alexander Lobakin wrote:
>>> From: Yue Haibing <yuehaibing@huawei.com>
>>> Date: Wed, 27 Aug 2025 12:00:27 +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.
>>>
>>> ...but bloat-o-meter stats would be nice to see here. I'm curious
>>> whether the object code got any changes or the compilers still just
>>> inline this function to both call sites.
> 
> On a x86_64, with allmodconfig:
> 
> ./scripts/bloat-o-meter -c net/ipv6/sit.o net/ipv6/sit-after.o
> add/remove: 2/0 grow/shrink: 1/1 up/down: 1770/-2152 (-382)
> Function                                     old     new   delta
> ipip6_tunnel_dst_find                          -    1697   +1697
> __pfx_ipip6_tunnel_dst_find                    -      64     +64
> ipip6_tunnel_xmit.isra.cold                   79      88      +9
> ipip6_tunnel_xmit.isra                      9910    7758   -2152

Oh okay, so it doesn't inline the function due to its size. Maybe it's
even better since we have a good object code reduction now and that
branch inside the func shouldn't hurt the performance much.

> Total: Before=70060, After=69678, chg -0.55%

Thanks,
Olek