slirp: Add support for stateless DHCPv6

Provide basic support for stateless DHCPv6 (see RFC 3736) so
that guests can also automatically boot via IPv6 with SLIRP
(for IPv6 network booting, see RFC 5970 for details).

Tested with:

    qemu-system-ppc64 -nographic -vga none -boot n -net nic \
        -net user,ipv6=yes,ipv4=no,tftp=/path/to/tftp,bootfile=ppc64.img
Signed-off-by: NThomas Huth <thuth@redhat.com>
Signed-off-by: NSamuel Thibault <samuel.thibault@ens-lyon.org>

slirp/Makefile.objs

 common-obj-y = cksum.o if.o ip_icmp.o ip6_icmp.o ip6_input.o ip6_output.o \
-               ip_input.o ip_output.o dnssearch.o
+               ip_input.o ip_output.o dnssearch.o dhcpv6.o
 common-obj-y += slirp.o mbuf.o misc.o sbuf.o socket.o tcp_input.o tcp_output.o
 common-obj-y += tcp_subr.o tcp_timer.o udp.o udp6.o bootp.o tftp.o arp_table.o \
                 ndp_table.o

slirp/dhcpv6.c

+/*
+ * SLIRP stateless DHCPv6
+ *
+ * We only support stateless DHCPv6, e.g. for network booting.
+ * See RFC 3315, RFC 3736, RFC 3646 and RFC 5970 for details.
+ *
+ * Copyright 2016 Thomas Huth, Red Hat Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License,
+ * or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "qemu/osdep.h"
+#include "qemu/log.h"
+#include "slirp.h"
+#include "dhcpv6.h"
+
+/* DHCPv6 message types */
+#define MSGTYPE_REPLY        7
+#define MSGTYPE_INFO_REQUEST 11
+
+/* DHCPv6 option types */
+#define OPTION_CLIENTID      1
+#define OPTION_IAADDR        5
+#define OPTION_ORO           6
+#define OPTION_DNS_SERVERS   23
+#define OPTION_BOOTFILE_URL  59
+
+struct requested_infos {
+    uint8_t *client_id;
+    int client_id_len;
+    bool want_dns;
+    bool want_boot_url;
+};
+
+/**
+ * Analyze the info request message sent by the client to see what data it
+ * provided and what it wants to have. The information is gathered in the
+ * "requested_infos" struct. Note that client_id (if provided) points into
+ * the odata region, thus the caller must keep odata valid as long as it
+ * needs to access the requested_infos struct.
+ */
+static int dhcpv6_parse_info_request(uint8_t *odata, int olen,
+                                     struct requested_infos *ri)
+{
+    int i, req_opt;
+
+    while (olen > 4) {
+        /* Parse one option */
+        int option = odata[0] << 8 | odata[1];
+        int len = odata[2] << 8 | odata[3];
+
+        if (len + 4 > olen) {
+            qemu_log_mask(LOG_GUEST_ERROR, "Guest sent bad DHCPv6 packet!\n");
+            return -E2BIG;
+        }
+
+        switch (option) {
+        case OPTION_IAADDR:
+            /* According to RFC3315, we must discard requests with IA option */
+            return -EINVAL;
+        case OPTION_CLIENTID:
+            if (len > 256) {
+                /* Avoid very long IDs which could cause problems later */
+                return -E2BIG;
+            }
+            ri->client_id = odata + 4;
+            ri->client_id_len = len;
+            break;
+        case OPTION_ORO:        /* Option request option */
+            if (len & 1) {
+                return -EINVAL;
+            }
+            /* Check which options the client wants to have */
+            for (i = 0; i < len; i += 2) {
+                req_opt = odata[4 + i] << 8 | odata[4 + i + 1];
+                switch (req_opt) {
+                case OPTION_DNS_SERVERS:
+                    ri->want_dns = true;
+                    break;
+                case OPTION_BOOTFILE_URL:
+                    ri->want_boot_url = true;
+                    break;
+                default:
+                    DEBUG_MISC((dfd, "dhcpv6: Unsupported option request %d\n",
+                                req_opt));
+                }
+            }
+            break;
+        default:
+            DEBUG_MISC((dfd, "dhcpv6 info req: Unsupported option %d, len=%d\n",
+                        option, len));
+        }
+
+        odata += len + 4;
+        olen -= len + 4;
+    }
+
+    return 0;
+}
+
+
+/**
+ * Handle information request messages
+ */
+static void dhcpv6_info_request(Slirp *slirp, struct sockaddr_in6 *srcsas,
+                                uint32_t xid, uint8_t *odata, int olen)
+{
+    struct requested_infos ri = { NULL };
+    struct sockaddr_in6 sa6, da6;
+    struct mbuf *m;
+    uint8_t *resp;
+
+    if (dhcpv6_parse_info_request(odata, olen, &ri) < 0) {
+        return;
+    }
+
+    m = m_get(slirp);
+    if (!m) {
+        return;
+    }
+    memset(m->m_data, 0, m->m_size);
+    m->m_data += IF_MAXLINKHDR;
+    resp = (uint8_t *)m->m_data + sizeof(struct ip6) + sizeof(struct udphdr);
+
+    /* Fill in response */
+    *resp++ = MSGTYPE_REPLY;
+    *resp++ = (uint8_t)(xid >> 16);
+    *resp++ = (uint8_t)(xid >> 8);
+    *resp++ = (uint8_t)xid;
+
+    if (ri.client_id) {
+        *resp++ = OPTION_CLIENTID >> 8;         /* option-code high byte */
+        *resp++ = OPTION_CLIENTID;              /* option-code low byte */
+        *resp++ = ri.client_id_len >> 8;        /* option-len high byte */
+        *resp++ = ri.client_id_len;             /* option-len low byte */
+        memcpy(resp, ri.client_id, ri.client_id_len);
+        resp += ri.client_id_len;
+    }
+    if (ri.want_dns) {
+        *resp++ = OPTION_DNS_SERVERS >> 8;      /* option-code high byte */
+        *resp++ = OPTION_DNS_SERVERS;           /* option-code low byte */
+        *resp++ = 0;                            /* option-len high byte */
+        *resp++ = 16;                           /* option-len low byte */
+        memcpy(resp, &slirp->vnameserver_addr6, 16);
+        resp += 16;
+    }
+    if (ri.want_boot_url) {
+        uint8_t *sa = slirp->vhost_addr6.s6_addr;
+        int slen, smaxlen;
+
+        *resp++ = OPTION_BOOTFILE_URL >> 8;     /* option-code high byte */
+        *resp++ = OPTION_BOOTFILE_URL;          /* option-code low byte */
+        smaxlen = (uint8_t *)m->m_data + IF_MTU - (resp + 2);
+        slen = snprintf((char *)resp + 2, smaxlen,
+                        "tftp://[%02x%02x:%02x%02x:%02x%02x:%02x%02x:"
+                                "%02x%02x:%02x%02x:%02x%02x:%02x%02x]/%s",
+                        sa[0], sa[1], sa[2], sa[3], sa[4], sa[5], sa[6], sa[7],
+                        sa[8], sa[9], sa[10], sa[11], sa[12], sa[13], sa[14],
+                        sa[15], slirp->bootp_filename);
+        slen = min(slen, smaxlen);
+        *resp++ = slen >> 8;                    /* option-len high byte */
+        *resp++ = slen;                         /* option-len low byte */
+        resp += slen;
+    }
+
+    sa6.sin6_addr = slirp->vhost_addr6;
+    sa6.sin6_port = DHCPV6_SERVER_PORT;
+    da6.sin6_addr = srcsas->sin6_addr;
+    da6.sin6_port = srcsas->sin6_port;
+    m->m_data += sizeof(struct ip6) + sizeof(struct udphdr);
+    m->m_len = resp - (uint8_t *)m->m_data;
+    udp6_output(NULL, m, &sa6, &da6);
+}
+
+/**
+ * Handle DHCPv6 messages sent by the client
+ */
+void dhcpv6_input(struct sockaddr_in6 *srcsas, struct mbuf *m)
+{
+    uint8_t *data = (uint8_t *)m->m_data + sizeof(struct udphdr);
+    int data_len = m->m_len - sizeof(struct udphdr);
+    uint32_t xid;
+
+    if (data_len < 4) {
+        return;
+    }
+
+    xid = ntohl(*(uint32_t *)data) & 0xffffff;
+
+    switch (data[0]) {
+    case MSGTYPE_INFO_REQUEST:
+        dhcpv6_info_request(m->slirp, srcsas, xid, &data[4], data_len - 4);
+        break;
+    default:
+        DEBUG_MISC((dfd, "dhcpv6_input: Unsupported message type 0x%x\n",
+                    data[0]));
+    }
+}

slirp/dhcpv6.h

+/*
+ * Definitions and prototypes for SLIRP stateless DHCPv6
+ *
+ * Copyright 2016 Thomas Huth, Red Hat Inc.
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2
+ * or later. See the COPYING file in the top-level directory.
+ */
+#ifndef SLIRP_DHCPV6_H
+#define SLIRP_DHCPV6_H
+
+#define DHCPV6_SERVER_PORT 547
+
+#define ALLDHCP_MULTICAST { .s6_addr = \
+                            { 0xff, 0x02, 0x00, 0x00,\
+                            0x00, 0x00, 0x00, 0x00,\
+                            0x00, 0x00, 0x00, 0x00,\
+                            0x00, 0x01, 0x00, 0x02 } }
+
+void dhcpv6_input(struct sockaddr_in6 *srcsas, struct mbuf *m);
+
+#endif

slirp/udp6.c

@@ -7,6 +7,7 @@
 #include "qemu-common.h"
 #include "slirp.h"
 #include "udp.h"
+#include "dhcpv6.h"
 
 void udp6_input(struct mbuf *m)
 {
@@ -61,7 +62,17 @@ void udp6_input(struct mbuf *m)
     lhost.sin6_addr = ip->ip_src;
     lhost.sin6_port = uh->uh_sport;
 
-    /* TODO handle DHCP/BOOTP */
+    /* handle DHCPv6 */
+    if (ntohs(uh->uh_dport) == DHCPV6_SERVER_PORT &&
+        (in6_equal(&ip->ip_dst, &slirp->vhost_addr6) ||
+         in6_equal(&ip->ip_dst, &(struct in6_addr)ALLDHCP_MULTICAST))) {
+        m->m_data += iphlen;
+        m->m_len -= iphlen;
+        dhcpv6_input(&lhost, m);
+        m->m_data -= iphlen;
+        m->m_len += iphlen;
+        goto bad;
+    }
 
     /* handle TFTP */
     if (ntohs(uh->uh_dport) == TFTP_SERVER &&