linux-kernel - [PATCH 3/3] netpoll: Extract IPv6 address retrieval function

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Message-Id: <20250618-netpoll_ip_ref-v1-3-c2ac00fe558f@debian.org>
Date: Wed, 18 Jun 2025 02:32:47 -0700
From: Breno Leitao <leitao@...ian.org>
To: "David S. Miller" <davem@...emloft.net>, 
 Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, 
 Paolo Abeni <pabeni@...hat.com>, Simon Horman <horms@...nel.org>
Cc: jv@...sburgh.ne, netdev@...r.kernel.org, linux-kernel@...r.kernel.org, 
 Breno Leitao <leitao@...ian.org>, gustavold@...il.com
Subject: [PATCH 3/3] netpoll: Extract IPv6 address retrieval function

Extract the IPv6 address retrieval logic from netpoll_setup() into
a dedicated helper function netpoll_take_ipv6() to improve code
organization and readability.

The function handles obtaining the local IPv6 address from the
network device, including proper address type matching between
local and remote addresses (link-local vs global), and includes
appropriate error handling when IPv6 is not supported or no
suitable address is available.

Signed-off-by: Breno Leitao <leitao@...ian.org>
---
 net/core/netpoll.c | 76 +++++++++++++++++++++++++++++++-----------------------
 1 file changed, 44 insertions(+), 32 deletions(-)

diff --git a/net/core/netpoll.c b/net/core/netpoll.c
index 6ab494559b5c6..7021ea45a0539 100644
--- a/net/core/netpoll.c
+++ b/net/core/netpoll.c
@@ -598,6 +598,47 @@ static void netpoll_wait_carrier(struct netpoll *np, struct net_device *ndev,
 	}
 }
 
+/*
+ * Take the IPv6 from ndev and populate local_ip structure in netpoll
+ */
+static int netpoll_take_ipv6(struct netpoll *np, struct net_device *ndev)
+{
+	char buf[MAC_ADDR_STR_LEN + 1];
+	int err = -EDESTADDRREQ;
+	struct inet6_dev *idev;
+
+	if (!IS_ENABLED(CONFIG_IPV6)) {
+		np_err(np, "IPv6 is not supported %s, aborting\n",
+		       egress_dev(np, buf));
+		return -EINVAL;
+	}
+
+	idev = __in6_dev_get(ndev);
+	if (idev) {
+		struct inet6_ifaddr *ifp;
+
+		read_lock_bh(&idev->lock);
+		list_for_each_entry(ifp, &idev->addr_list, if_list) {
+			if (!!(ipv6_addr_type(&ifp->addr) & IPV6_ADDR_LINKLOCAL) !=
+				!!(ipv6_addr_type(&np->remote_ip.in6) & IPV6_ADDR_LINKLOCAL))
+				continue;
+			/* Got the IP, let's return */
+			np->local_ip.in6 = ifp->addr;
+			err = 0;
+			break;
+		}
+		read_unlock_bh(&idev->lock);
+	}
+	if (err) {
+		np_err(np, "no IPv6 address for %s, aborting\n",
+		       egress_dev(np, buf));
+		return err;
+	}
+
+	np_info(np, "local IPv6 %pI6c\n", &np->local_ip.in6);
+	return 0;
+}
+
 /*
  * Take the IPv4 from ndev and populate local_ip structure in netpoll
  */
@@ -675,41 +716,12 @@ int netpoll_setup(struct netpoll *np)
 			err = netpoll_take_ipv4(np, ndev);
 			if (err)
 				goto put;
-			ip_overwritten = true;
 		} else {
-#if IS_ENABLED(CONFIG_IPV6)
-			struct inet6_dev *idev;
-
-			err = -EDESTADDRREQ;
-			idev = __in6_dev_get(ndev);
-			if (idev) {
-				struct inet6_ifaddr *ifp;
-
-				read_lock_bh(&idev->lock);
-				list_for_each_entry(ifp, &idev->addr_list, if_list) {
-					if (!!(ipv6_addr_type(&ifp->addr) & IPV6_ADDR_LINKLOCAL) !=
-					    !!(ipv6_addr_type(&np->remote_ip.in6) & IPV6_ADDR_LINKLOCAL))
-						continue;
-					np->local_ip.in6 = ifp->addr;
-					ip_overwritten = true;
-					err = 0;
-					break;
-				}
-				read_unlock_bh(&idev->lock);
-			}
-			if (err) {
-				np_err(np, "no IPv6 address for %s, aborting\n",
-				       egress_dev(np, buf));
+			err = netpoll_take_ipv6(np, ndev);
+			if (err)
 				goto put;
-			} else
-				np_info(np, "local IPv6 %pI6c\n", &np->local_ip.in6);
-#else
-			np_err(np, "IPv6 is not supported %s, aborting\n",
-			       egress_dev(np, buf));
-			err = -EINVAL;
-			goto put;
-#endif
 		}
+		ip_overwritten = true;
 	}
 
 	err = __netpoll_setup(np, ndev);

-- 
2.47.1