If ipv6 auto-configuration does not work, currently it's hard
to track what's going on. This change adds log messages
(at debug level) on every code path where ipv6 autoconf fails.

v3: changed pr_debug's to pr_warn's.

Signed-off-by: Denys Vlasenko <dvlas...@redhat.com>
---
 net/ipv6/addrconf.c | 45 ++++++++++++++++++++++++++++++++++++---------
 1 file changed, 36 insertions(+), 9 deletions(-)

diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index 3c3425e..0b354f0 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -1694,8 +1694,11 @@ static void addrconf_leave_anycast(struct inet6_ifaddr 
*ifp)
 
 static int addrconf_ifid_eui48(u8 *eui, struct net_device *dev)
 {
-       if (dev->addr_len != ETH_ALEN)
+       if (dev->addr_len != ETH_ALEN) {
+               pr_warn("IPv6 addrconf: %s: address length %d != %s\n",
+                       dev->name, dev->addr_len, "ETH_ALEN");
                return -1;
+       }
        memcpy(eui, dev->dev_addr, 3);
        memcpy(eui + 5, dev->dev_addr + 3, 3);
 
@@ -1725,8 +1728,11 @@ static int addrconf_ifid_eui48(u8 *eui, struct 
net_device *dev)
 
 static int addrconf_ifid_eui64(u8 *eui, struct net_device *dev)
 {
-       if (dev->addr_len != IEEE802154_ADDR_LEN)
+       if (dev->addr_len != IEEE802154_ADDR_LEN) {
+               pr_warn("IPv6 addrconf: %s: address length %d != %s\n",
+                       dev->name, dev->addr_len, "IEEE802154_ADDR_LEN");
                return -1;
+       }
        memcpy(eui, dev->dev_addr, 8);
        eui[0] ^= 2;
        return 0;
@@ -1736,8 +1742,11 @@ static int addrconf_ifid_ieee1394(u8 *eui, struct 
net_device *dev)
 {
        union fwnet_hwaddr *ha;
 
-       if (dev->addr_len != FWNET_ALEN)
+       if (dev->addr_len != FWNET_ALEN) {
+               pr_warn("IPv6 addrconf: %s: address length %d != %s\n",
+                       dev->name, dev->addr_len, "FWNET_ALEN");
                return -1;
+       }
 
        ha = (union fwnet_hwaddr *)dev->dev_addr;
 
@@ -1749,8 +1758,11 @@ static int addrconf_ifid_ieee1394(u8 *eui, struct 
net_device *dev)
 static int addrconf_ifid_arcnet(u8 *eui, struct net_device *dev)
 {
        /* XXX: inherit EUI-64 from other interface -- yoshfuji */
-       if (dev->addr_len != ARCNET_ALEN)
+       if (dev->addr_len != ARCNET_ALEN) {
+               pr_warn("IPv6 addrconf: %s: address length %d != %s\n",
+                       dev->name, dev->addr_len, "ARCNET_ALEN");
                return -1;
+       }
        memset(eui, 0, 7);
        eui[7] = *(u8 *)dev->dev_addr;
        return 0;
@@ -1758,17 +1770,25 @@ static int addrconf_ifid_arcnet(u8 *eui, struct 
net_device *dev)
 
 static int addrconf_ifid_infiniband(u8 *eui, struct net_device *dev)
 {
-       if (dev->addr_len != INFINIBAND_ALEN)
+       if (dev->addr_len != INFINIBAND_ALEN) {
+               pr_warn("IPv6 addrconf: %s: address length %d != %s\n",
+                       dev->name, dev->addr_len, "INFINIBAND_ALEN");
                return -1;
+       }
        memcpy(eui, dev->dev_addr + 12, 8);
        eui[0] |= 2;
        return 0;
 }
 
-static int __ipv6_isatap_ifid(u8 *eui, __be32 addr)
+static int __ipv6_isatap_ifid(u8 *eui, struct net_device *dev)
 {
-       if (addr == 0)
+       __be32 addr = *(__be32 *)dev->dev_addr;
+
+       if (addr == 0) {
+               pr_warn("IPv6 addrconf: %s: bad dev_addr %pM\n",
+                       dev->name, dev->dev_addr);
                return -1;
+       }
        eui[0] = (ipv4_is_zeronet(addr) || ipv4_is_private_10(addr) ||
                  ipv4_is_loopback(addr) || ipv4_is_linklocal_169(addr) ||
                  ipv4_is_private_172(addr) || ipv4_is_test_192(addr) ||
@@ -1785,13 +1805,14 @@ static int __ipv6_isatap_ifid(u8 *eui, __be32 addr)
 static int addrconf_ifid_sit(u8 *eui, struct net_device *dev)
 {
        if (dev->priv_flags & IFF_ISATAP)
-               return __ipv6_isatap_ifid(eui, *(__be32 *)dev->dev_addr);
+               return __ipv6_isatap_ifid(eui, dev);
+       pr_warn("IPv6 addrconf: %s: IFF_ISATAP is unset\n", dev->name);
        return -1;
 }
 
 static int addrconf_ifid_gre(u8 *eui, struct net_device *dev)
 {
-       return __ipv6_isatap_ifid(eui, *(__be32 *)dev->dev_addr);
+       return __ipv6_isatap_ifid(eui, dev);
 }
 
 static int addrconf_ifid_ip6tnl(u8 *eui, struct net_device *dev)
@@ -1825,6 +1846,8 @@ static int ipv6_generate_eui64(u8 *eui, struct net_device 
*dev)
        case ARPHRD_TUNNEL6:
                return addrconf_ifid_ip6tnl(eui, dev);
        }
+       pr_warn("IPv6 addrconf: %s: dev->type %d is not supported\n",
+               dev->name, dev->type);
        return -1;
 }
 
@@ -1842,6 +1865,10 @@ static int ipv6_inherit_eui64(u8 *eui, struct inet6_dev 
*idev)
                }
        }
        read_unlock_bh(&idev->lock);
+       if (err)
+               pr_warn("IPv6 addrconf: "
+                       "%s: no link-local address to inherit\n",
+                       idev->dev->name);
        return err;
 }
 
-- 
1.8.1.4

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