[PATCH bpf-next] bpf: Fix unused nskb warning in bpf_icmp_send

[Mahe Tardy]

Declare nskb inside the IPv4 and IPv6 case blocks so it is only present
when the corresponding code is built. The case braces are intentional to
scope the local declarations under the switch labels.

Fixes: f3603df9aebb ("bpf: Add bpf_icmp_send kfunc")
Reported-by: kernel test robot <lkp@xxxxxxxxx>
Closes: https://lore.kernel.org/oe-kbuild-all/202607110140.JeJZ6GIa-lkp@xxxxxxxxx/
Signed-off-by: Mahe Tardy <mahe.tardy@xxxxxxxxx>
---
 net/core/filter.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/net/core/filter.c b/net/core/filter.c
index e4697036c67b..056deb9b3fc3 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -12575,7 +12575,6 @@ __bpf_kfunc int bpf_xdp_pull_data(struct xdp_md *x, u32 len)
 __bpf_kfunc int bpf_icmp_send(struct __sk_buff *skb_ctx, int type, int code)
 {
 	struct sk_buff *skb = (struct sk_buff *)skb_ctx;
-	struct sk_buff *nskb;
 	struct sock *sk;

 	sk = skb_to_full_sk(skb);
@@ -12589,6 +12588,8 @@ __bpf_kfunc int bpf_icmp_send(struct __sk_buff *skb_ctx, int type, int code)
 	switch (skb->protocol) {
 #if IS_ENABLED(CONFIG_INET)
 	case htons(ETH_P_IP): {
+		struct sk_buff *nskb;
+
 		if (type != ICMP_DEST_UNREACH)
 			return -EOPNOTSUPP;
 		if (code < 0 || code > NR_ICMP_UNREACH ||
@@ -12606,7 +12607,9 @@ __bpf_kfunc int bpf_icmp_send(struct __sk_buff *skb_ctx, int type, int code)
 	}
 #endif
 #if IS_ENABLED(CONFIG_IPV6)
-	case htons(ETH_P_IPV6):
+	case htons(ETH_P_IPV6): {
+		struct sk_buff *nskb;
+
 		if (type != ICMPV6_DEST_UNREACH)
 			return -EOPNOTSUPP;
 		if (code < 0 || code > ICMPV6_REJECT_ROUTE)
@@ -12620,6 +12623,7 @@ __bpf_kfunc int bpf_icmp_send(struct __sk_buff *skb_ctx, int type, int code)
 		icmpv6_send(nskb, type, code, 0);
 		consume_skb(nskb);
 		break;
+	}
 #endif
 	default:
 		return -EPROTONOSUPPORT;
--
2.34.1