slirp: Add RDNSS advertisement

This adds the RDNSS option to IPv6 router advertisements, so that the guest
can autoconfigure the DNS server address.

Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
Reviewed-by: Thomas Huth <thuth@redhat.com>

---
Changes since last submission:
- Disable on windows, until we have support for it

2 files changed, 35 insertions, 6 deletions

diff --git a/ip6_icmp.c b/ip6_icmp.c
index 4da3ca0..42fc6dc 100644
--- a/ip6_icmp.c
+++ b/ip6_icmp.c
@@ -146,8 +146,12 @@ void ndp_send_ra(Slirp *slirp)
     rip->ip_src = (struct in6_addr)LINKLOCAL_ADDR;
     rip->ip_dst = (struct in6_addr)ALLNODES_MULTICAST;
     rip->ip_nh = IPPROTO_ICMPV6;
-    rip->ip_pl = htons(ICMP6_NDP_RA_MINLEN + NDPOPT_LINKLAYER_LEN +
-                       NDPOPT_PREFIXINFO_LEN);
+    rip->ip_pl =
+        htons(ICMP6_NDP_RA_MINLEN + NDPOPT_LINKLAYER_LEN + NDPOPT_PREFIXINFO_LEN
+#ifndef _WIN32
+              + NDPOPT_RDNSS_LEN
+#endif
+        );
     t->m_len = sizeof(struct ip6) + ntohs(rip->ip_pl);
 
     /* Build ICMPv6 packet */
@@ -165,16 +169,16 @@ void ndp_send_ra(Slirp *slirp)
     ricmp->icmp6_nra.lifetime = htons(NDP_AdvDefaultLifetime);
     ricmp->icmp6_nra.reach_time = htonl(NDP_AdvReachableTime);
     ricmp->icmp6_nra.retrans_time = htonl(NDP_AdvRetransTime);
+    t->m_data += ICMP6_NDP_RA_MINLEN;
 
     /* Source link-layer address (NDP option) */
-    t->m_data += ICMP6_NDP_RA_MINLEN;
     struct ndpopt *opt = mtod(t, struct ndpopt *);
     opt->ndpopt_type = NDPOPT_LINKLAYER_SOURCE;
     opt->ndpopt_len = NDPOPT_LINKLAYER_LEN / 8;
     in6_compute_ethaddr(rip->ip_src, opt->ndpopt_linklayer);
+    t->m_data += NDPOPT_LINKLAYER_LEN;
 
     /* Prefix information (NDP option) */
-    t->m_data += NDPOPT_LINKLAYER_LEN;
     struct ndpopt *opt2 = mtod(t, struct ndpopt *);
     opt2->ndpopt_type = NDPOPT_PREFIX_INFO;
     opt2->ndpopt_len = NDPOPT_PREFIXINFO_LEN / 8;
@@ -186,8 +190,25 @@ void ndp_send_ra(Slirp *slirp)
     opt2->ndpopt_prefixinfo.pref_lt = htonl(NDP_AdvPrefLifetime);
     opt2->ndpopt_prefixinfo.reserved2 = 0;
     opt2->ndpopt_prefixinfo.prefix = slirp->vprefix_addr6;
+    t->m_data += NDPOPT_PREFIXINFO_LEN;
+
+#ifndef _WIN32
+    /* Prefix information (NDP option) */
+    /* disabled for windows for now, until get_dns6_addr is implemented */
+    struct ndpopt *opt3 = mtod(t, struct ndpopt *);
+    opt3->ndpopt_type = NDPOPT_RDNSS;
+    opt3->ndpopt_len = NDPOPT_RDNSS_LEN / 8;
+    opt3->ndpopt_rdnss.reserved = 0;
+    opt3->ndpopt_rdnss.lifetime = htonl(2 * NDP_MaxRtrAdvInterval);
+    opt3->ndpopt_rdnss.addr = slirp->vnameserver_addr6;
+    t->m_data += NDPOPT_RDNSS_LEN;
+#endif
 
     /* ICMPv6 Checksum */
+#ifndef _WIN32
+    t->m_data -= NDPOPT_RDNSS_LEN;
+#endif
+    t->m_data -= NDPOPT_PREFIXINFO_LEN;
     t->m_data -= NDPOPT_LINKLAYER_LEN;
     t->m_data -= ICMP6_NDP_RA_MINLEN;
     t->m_data -= sizeof(struct ip6);
diff --git a/ip6_icmp.h b/ip6_icmp.h
index 99a369f..da91dd0 100644
--- a/ip6_icmp.h
+++ b/ip6_icmp.h
@@ -109,6 +109,7 @@ struct ndpopt {
     uint8_t ndpopt_len; /* /!\ In units of 8 octets */
     union {
         unsigned char linklayer_addr[6]; /* Source/Target Link-layer */
+#define ndpopt_linklayer ndpopt_body.linklayer_addr
         struct prefixinfo { /* Prefix Information */
             uint8_t prefix_length;
 #ifdef HOST_WORDS_BIGENDIAN
@@ -121,19 +122,26 @@ struct ndpopt {
             uint32_t reserved2;
             struct in6_addr prefix;
         } QEMU_PACKED prefixinfo;
-    } ndpopt_body;
-#define ndpopt_linklayer ndpopt_body.linklayer_addr
 #define ndpopt_prefixinfo ndpopt_body.prefixinfo
+        struct rdnss {
+            uint16_t reserved;
+            uint32_t lifetime;
+            struct in6_addr addr;
+        } QEMU_PACKED rdnss;
+#define ndpopt_rdnss ndpopt_body.rdnss
+    } ndpopt_body;
 } QEMU_PACKED;
 
 /* NDP options type */
 #define NDPOPT_LINKLAYER_SOURCE 1 /* Source Link-Layer Address */
 #define NDPOPT_LINKLAYER_TARGET 2 /* Target Link-Layer Address */
 #define NDPOPT_PREFIX_INFO 3 /* Prefix Information */
+#define NDPOPT_RDNSS 25 /* Recursive DNS Server Address */
 
 /* NDP options size, in octets. */
 #define NDPOPT_LINKLAYER_LEN 8
 #define NDPOPT_PREFIXINFO_LEN 32
+#define NDPOPT_RDNSS_LEN 24
 
 /*
  * Definition of type and code field values.