NLM: Support IPv6 scope IDs in nlm_display_address()

Scope ID support is needed since the kernel's NSM implementation is
about to use these displayed addresses as a mon_name in some cases.

When nsm_use_hostnames is zero, without scope ID support NSM will fail
to handle peers that contact us via a link-local address.  Link-local
addresses do not work without an interface ID, which is stored in the
sockaddr's sin6_scope_id field.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>

2 files changed, 24 insertions, 7 deletions

diff --git a/fs/lockd/host.c b/fs/lockd/host.c
index beb5da810167..012e49aaecd1 100644
--- a/fs/lockd/host.c
+++ b/fs/lockd/host.c
@@ -105,22 +105,31 @@ static void nlm_clear_port(struct sockaddr *sap)
         }
 }
 
+static void nlm_display_ipv6_address(const struct sockaddr *sap, char *buf,
+                                     const size_t len)
+{
+        const struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *)sap;
+
+        if (ipv6_addr_v4mapped(&sin6->sin6_addr))
+                snprintf(buf, len, "%pI4", &sin6->sin6_addr.s6_addr32[3]);
+        else if (sin6->sin6_scope_id != 0)
+                snprintf(buf, len, "%pI6%%%u", &sin6->sin6_addr,
+                                sin6->sin6_scope_id);
+        else
+                snprintf(buf, len, "%pI6", &sin6->sin6_addr);
+}
+
 static void nlm_display_address(const struct sockaddr *sap,
                                 char *buf, const size_t len)
 {
         const struct sockaddr_in *sin = (struct sockaddr_in *)sap;
-        const struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *)sap;
 
         switch (sap->sa_family) {
         case AF_INET:
                 snprintf(buf, len, "%pI4", &sin->sin_addr.s_addr);
                 break;
         case AF_INET6:
-                if (ipv6_addr_v4mapped(&sin6->sin6_addr))
-                        snprintf(buf, len, "%pI4",
-                                 &sin6->sin6_addr.s6_addr32[3]);
-                else
-                        snprintf(buf, len, "%pI6", &sin6->sin6_addr);
+                nlm_display_ipv6_address(sap, buf, len);
                 break;
         default:
                 snprintf(buf, len, "unsupported address family");
diff --git a/include/linux/lockd/lockd.h b/include/linux/lockd/lockd.h
index dae22cb4c38d..80a0a2cff2b8 100644
--- a/include/linux/lockd/lockd.h
+++ b/include/linux/lockd/lockd.h
@@ -68,6 +68,14 @@ struct nlm_host {
         char                    *h_addrbuf;     /* address eyecatcher */
 };
 
+/*
+ * The largest string sm_addrbuf should hold is a full-size IPv6 address
+ * (no "::" anywhere) with a scope ID.  The buffer size is computed to
+ * hold eight groups of colon-separated four-hex-digit numbers, a
+ * percent sign, a scope id (at most 32 bits, in decimal), and NUL.
+ */
+#define NSM_ADDRBUF             ((8 * 4 + 7) + (1 + 10) + 1)
+
 struct nsm_handle {
         struct list_head        sm_link;
         atomic_t                sm_count;
@@ -76,7 +84,7 @@ struct nsm_handle {
         size_t                  sm_addrlen;
         unsigned int            sm_monitored : 1,
                                 sm_sticky : 1;  /* don't unmonitor */
-        char                    sm_addrbuf[48]; /* address eyecatcher */
+        char                    sm_addrbuf[NSM_ADDRBUF];
 };
 
 /*