Changeset 59142 in vbox for trunk/src/VBox/Devices/Network/slirp

Timestamp:

Dec 15, 2015 11:12:29 PM (9 years ago)

Author:

vboxsync

Message:

NAT: Start rewriting host resolver to clean up the code to be able to
add reverse lookups eventually. Name compression (label pointers) are
supported in replies. Code for user-defined mapping is left as is for
now.

Location:

trunk/src/VBox/Devices/Network/slirp

Files:

• hostres.c (modified) (1 diff)
• slirp.h (modified) (1 diff)

trunk/src/VBox/Devices/Network/slirp/hostres.c

@@ -28 +28 @@
 #define DNS_CONTROL_PORT_NUMBER 53
 /* see RFC 1035(4.1.1) */
-union dnsmsg_header
-{
-    struct
-    {
-        unsigned id:16;
-        unsigned rd:1;
-        unsigned tc:1;
-        unsigned aa:1;
-        unsigned opcode:4;
-        unsigned qr:1;
-        unsigned rcode:4;
-        unsigned Z:3;
-        unsigned ra:1;
-        uint16_t qdcount;
-        uint16_t ancount;
-        uint16_t nscount;
-        uint16_t arcount;
-    } X;
-    uint16_t raw[6];
+struct dnsmsg_header
+{
+    uint16_t id;
+
+    /* XXX: endianness */
+    unsigned rd:1;
+    unsigned tc:1;
+    unsigned aa:1;
+    unsigned opcode:4;
+    unsigned qr:1;
+    unsigned rcode:4;
+    unsigned Z:3;
+    unsigned ra:1;
+
+    uint16_t qdcount;
+    uint16_t ancount;
+    uint16_t nscount;
+    uint16_t arcount;
 };
-AssertCompileSize(union dnsmsg_header, 12);
-
-struct dns_meta_data
-{
-    uint16_t type;
-    uint16_t class;
+AssertCompileSize(struct dnsmsg_header, 12);
+
+#define QR_Query                0
+#define QR_Response             1
+
+#define OpCode_Query            0
+
+#define RCode_NoError           0
+#define RCode_FormErr           1
+#define RCode_ServFail          2
+#define RCode_NXDomain          3
+#define RCode_NotImp            4
+#define RCode_Refused           5
+
+#define Type_A                  1
+#define Type_CNAME              5
+#define Type_PTR                12
+#define Type_ANY                255
+
+#define Class_IN                1
+#define Class_ANY               255
+
+/* compressed label encoding */
+#define DNS_LABEL_PTR           0xc0
+
+#define DNS_MAX_UDP_LEN         512
+#define DNS_MAX_LABEL_LEN       63
+#define DNS_MAX_NAME_LEN        255
+
+
+/*
+ * A tree of labels.
+ *
+ * rfc1035#section-3.1
+ * rfc1035#section-4.1.4
+ */
+struct label
+{
+    const uint8_t *buf;
+    ssize_t off;
+    struct label *children;
+    struct label *sibling;
 };
 
-struct dnsmsg_answer
-{
-    uint16_t name;
-    struct dns_meta_data meta;
-    uint16_t ttl[2];
-    uint16_t rdata_len;
-    uint8_t  rdata[1];  /* depends on value at rdata_len */
+
+/*
+ * A structure to build DNS response.
+ */
+struct response
+{
+    struct label *labels;       /* already encoded in buf */
+    size_t qlen;                /* original question */
+    size_t end;                 /* of data in buf */
+
+    /* continuous buffer to build the response */
+    uint8_t buf[DNS_MAX_UDP_LEN];
 };
 
-/* see RFC 1035(4.1) */
-static void CStr2QStr(const char *pcszStr, char *pszQStr, size_t cQStr);
-static void QStr2CStr(const char *pcszQStr, char *pszStr, size_t cStr);
+
+static int verify_header(PNATState pData, struct mbuf **pMBuf);
+static struct mbuf *respond(PNATState pData, struct mbuf *m, struct response *res);
+struct mbuf *resolve(PNATState pData, struct mbuf *m, struct response *res, size_t qname, uint16_t qtype);
+struct mbuf *refuse(PNATState pData, struct mbuf *m, unsigned int rcode);
+static ssize_t append_a(struct response *res, const char *name, struct in_addr addr);
+static ssize_t append_cname(struct response *res, const char *name, const char *cname);
+static ssize_t append_rrhdr(struct response *res, const char *name, uint16_t type, uint32_t ttl);
+static ssize_t append_name(struct response *res, const char *name);
+static ssize_t append_u32(struct response *res, uint32_t value);
+static ssize_t append_u16(struct response *res, uint16_t value);
+static ssize_t append_u8(struct response *res, uint8_t value);
+static ssize_t append_bytes(struct response *res, uint8_t *p, size_t size);
+static ssize_t check_space(struct response *res, size_t size);
+
+static void strnlabels(char *namebuf, size_t nbuflen, const uint8_t *msg, size_t off);
+
+static void LogLabelsTree(const char *before, struct label *l, const char *after);
+static void free_labels(struct label *root);
+
 #ifdef VBOX_WITH_DNSMAPPING_IN_HOSTRESOLVER
 static void alterHostentWithDataFromDNSMap(PNATState pData, struct hostent *pHostent);
 #endif
 
-
+#if 1 /* XXX */
+# define LogErr(args) Log2(args)
+# define LogDbg(args) Log3(args)
+#else
+# define LogErr(args) LogRel(args)
+# define LogDbg(args) LogRel(args)
+#endif
+
+
+struct mbuf *
+hostresolver(PNATState pData, struct mbuf *m)
+{
+    struct label *l;
+    int error;
+
+    struct response res;
+
+    error = verify_header(pData, &m);
+    if (error != 0)
+        return m;
+
+    RT_ZERO(res);
+
+    /*
+     * Do the real work
+     */
+    m = respond(pData, m, &res);
+
+    free_labels(res.labels);
+    return m;
+}
+
+
+struct mbuf *
+refuse(PNATState pData, struct mbuf *m, unsigned int rcode)
+{
+    struct dnsmsg_header *pHdr;
+
+    pHdr = mtod(m, struct dnsmsg_header *);
+    pHdr->qr = QR_Response;
+    pHdr->rcode = rcode;
+    pHdr->ra = 1;
+    pHdr->aa = 0;
+
+    return m;
+}
+
+
+static int
+verify_header(PNATState pData, struct mbuf **pMBuf)
+{
+    struct mbuf *m;
+    struct dnsmsg_header *pHdr;
+    size_t mlen;
+
+    m = *pMBuf;
+
+    /*
+     * In theory we should have called
+     *
+     *   m = m_pullup(m, sizeof(struct dnsmsg_header));
+     *
+     * here first (which should have been a nop), but the way mbufs
+     * are used in NAT will always cause a copy that will have no
+     * leading space.  We can use m_copyup() instead, but if we are
+     * peeking under the hood anyway, we might as well just rely on
+     * the fact that this header will be contiguous.
+     */
+    pHdr = mtod(m, struct dnsmsg_header *);
+
+    if (RT_UNLIKELY(pHdr->qr != QR_Query))
+    {
+        LogErr(("NAT: hostres: unexpected response\n"));
+        goto drop;
+    }
+
+    mlen = m_length(m, NULL);
+    if (RT_UNLIKELY(mlen > DNS_MAX_UDP_LEN))
+    {
+        LogErr(("NAT: hostres: packet too large\n"));
+        refuse(pData, m, RCode_FormErr); /* or drop? */
+        return 1;
+    }
+
+    if (RT_UNLIKELY(pHdr->opcode != OpCode_Query))
+    {
+        LogErr(("NAT: hostres: unsupported opcode\n"));
+        refuse(pData, m, RCode_NotImp);
+        return 1;
+    }
+
+    if (RT_UNLIKELY(pHdr->Z != 0))
+    {
+        LogErr(("NAT: hostres: MBZ bits are not\n"));
+        refuse(pData, m, RCode_FormErr);
+        return 1;
+    }
+
+    if (RT_UNLIKELY(pHdr->qdcount != RT_H2N_U16_C(1)))
+    {
+        LogErr(("NAT: hostres: multiple questions\n"));
+        refuse(pData, m, RCode_NotImp);
+        return 1;
+    }
+
+    if (RT_UNLIKELY(pHdr->ancount != 0))
+    {
+        LogErr(("NAT: hostres: answers in query\n"));
+        refuse(pData, m, RCode_FormErr);
+        return 1;
+    }
+
+    if (RT_UNLIKELY(pHdr->nscount != 0))
+    {
+        LogErr(("NAT: hostres: authority RRs in query\n"));
+        refuse(pData, m, RCode_FormErr);
+        return 1;
+    }
+
+    if (RT_UNLIKELY(pHdr->arcount != 0))
+    {
+        LogErr(("NAT: hostres: additional info RRs in query\n"));
+        refuse(pData, m, RCode_FormErr);
+        return 1;
+    }
+
+    if (RT_UNLIKELY(mlen < sizeof(*pHdr)
+                             + /* qname  */ 1
+                             + /* qtype  */ 2
+                             + /* qclass */ 2))
+    {
+        LogErr(("NAT: hostres: packet too small\n"));
+        refuse(pData, m, RCode_FormErr);
+        return 1;
+    }
+
+    return 0;
+
+  drop:
+    if (m != NULL)
+        m_freem(pData, m);
+    *pMBuf = NULL;
+    return 1;
+}
+
+
+static struct mbuf *
+respond(PNATState pData, struct mbuf *m, struct response *res)
+{
+    struct dnsmsg_header *pHdr;
+    size_t mlen;
+    size_t off;
+    size_t qname;
+    uint16_t qtype, qclass;
+    struct label *l, **pparent;
+
+    /**
+     * Copy the request into the contiguous buffer for the response
+     * and parse the question.
+     */
+
+    mlen = m_length(m, NULL);
+    m_copydata(m, 0, mlen, (char *)res->buf);
+    res->end = res->qlen = mlen;
+
+    /* convert header to response */
+    pHdr = (struct dnsmsg_header *)res->buf;
+    pHdr->qr = QR_Response;
+    pHdr->rcode = RCode_NoError;
+    pHdr->ra = 1;               /* the host provides recursion */
+    pHdr->aa = 0;               /* we are not authoritative */
+
+    off = sizeof(*pHdr);
+    qname = off;
+
+    /*
+     * Parse/verify QNAME and collect the suffixes to be used for
+     * compression in the answer.
+     */
+    while (off < mlen) {
+        size_t loff, llen;
+        uint8_t c;
+
+        c = res->buf[off];
+
+        /*
+         * There's just one question with just one name, so there are
+         * no other labels it can point to.  Thus all well-formed
+         * names with a pointer can only be infinite loops.
+         */
+        if ((c & DNS_LABEL_PTR) == DNS_LABEL_PTR)
+        {
+            LogErr(("NAT: hostres: label pointer in the qname\n"));
+            return refuse(pData, m, RCode_FormErr);
+        }
+
+        if ((c & DNS_LABEL_PTR) != 0)
+        {
+            LogErr(("NAT: hostres: unexpected high bits\n"));
+            return refuse(pData, m, RCode_FormErr);
+        }
+
+        /*
+         * label of "llen" chars starts at offset "loff".
+         */
+        loff = off;
+        llen = c;
+        ++off;
+
+        if (loff + 1 + llen > mlen)
+        {
+            LogErr(("NAT: hostres: length byte points beyound packet boundary\n"));
+            return refuse(pData, m, RCode_FormErr);
+        }
+
+        if (llen == 0)             /* end of the label list */
+        {
+            break;
+        }
+
+        /* do only minimal verification of the label */
+        while (off < loff + 1 + llen)
+        {
+            c = res->buf[off];
+            ++off;
+
+            if (c == '.')
+            {
+                LogErr(("NAT: hostres: dot inside label\n"));
+                return refuse(pData, m, RCode_FormErr);
+            }
+
+            if (c == '\0')
+            {
+                LogErr(("NAT: hostres: nul byte inside label\n"));
+                return refuse(pData, m, RCode_FormErr);
+            }
+        }
+
+        l = RTMemAllocZ(sizeof(*l));
+        l->buf = res->buf;
+        l->off = loff;
+        l->children = res->labels;
+        res->labels = l;
+    }
+
+    /*
+     * QTYPE and QCLASS
+     */
+    if (RT_UNLIKELY(off + 4 != mlen))
+    {
+        LogErr(("NAT: hostres: question too short / too long\n"));
+        return refuse(pData, m, RCode_FormErr);
+    }
+
+    memcpy(&qtype, &res->buf[off], sizeof(qtype));
+    qtype = RT_N2H_U16(qtype);
+    off += sizeof(qtype);
+
+    memcpy(&qclass, &res->buf[off], sizeof(qclass));
+    qclass = RT_N2H_U16(qclass);
+    off += sizeof(qclass);
+
+    if (   qclass != Class_IN
+        && qclass != Class_ANY)
+    {
+        LogErr(("NAT: hostres: unsupported qclass %d\n", qclass));
+        return refuse(pData, m, RCode_NotImp);
+    }
+
+    if (   qtype != Type_A
+        && qtype != Type_ANY)
+    {
+        LogErr(("NAT: hostres: unsupported qtype %d\n", qtype));
+        return refuse(pData, m, RCode_NotImp);
+    }
+
+    return resolve(pData, m, res, qname, qtype);
+}
+
+
+struct mbuf *
+resolve(PNATState pData, struct mbuf *m, struct response *res,
+        size_t qname, uint16_t qtype)
+{
+    struct dnsmsg_header *pHdr;
+    struct hostent *h;
+    size_t oend;
+    size_t nanswers;
+    ssize_t nbytes;
+    int i;
+
+    char name[DNS_MAX_NAME_LEN+1];
+
+    pHdr = (struct dnsmsg_header *)res->buf;
+    nanswers = 0;
+    oend = res->end;
+
+    strnlabels(name, sizeof(name), res->buf, qname);
+    LogDbg(("NAT: hostres: qname=\"%s\"\n", name));
+
+    h = gethostbyname(name);
+    if (h == NULL)
+    {
+        /* LogErr: h_errno */
+        return refuse(pData, m, RCode_NXDomain);
+    }
+
+#ifdef VBOX_WITH_DNSMAPPING_IN_HOSTRESOLVER
+    if (!LIST_EMPTY(&pData->DNSMapHead))
+        alterHostentWithDataFromDNSMap(pData, h);
+#endif
+
+    if (   h->h_name != NULL
+        && RTStrICmp(h->h_name, name) != 0)
+    {
+        LogDbg(("NAT: hostres: %s CNAME %s\n", name, h->h_name));
+        nbytes = append_cname(res, name, h->h_name);
+        if (nbytes > 0)
+        {
+            ++nanswers;
+        }
+        else
+        {
+            LogErr(("NAT: hostres: failed to add %s CNAME %s\n",
+                    name, h->h_name));
+            if (nbytes < 0)
+                return refuse(pData, m, RCode_ServFail);
+            else
+            {
+                pHdr->tc = 1;
+                goto out;
+            }
+        }
+    }
+
+    /*
+     * XXX: TODO: rfc1034#section-3.6.2
+     *
+     * If the query is Type_ANY and the name is CNAME, we should only
+     * return the CNAME, but not the A RRs.
+     */
+    for (i = 0; h->h_addr_list[i] != NULL; ++i)
+    {
+        const char *cname = h->h_name ? h->h_name : name;
+        struct in_addr addr;
+
+        addr.s_addr = *(uint32_t *)h->h_addr_list[i];
+        nbytes = append_a(res, cname, addr);
+
+        if (nbytes > 0)
+        {
+            ++nanswers;
+        }
+        else
+        {
+            LogErr(("NAT: hostres: failed to add %s A %RTnaipv4\n",
+                    cname, addr.s_addr));
+            if (nbytes < 0)
+                return refuse(pData, m, RCode_ServFail);
+            else
+            {
+                pHdr->tc = 1;
+                goto out;
+            }
+        }
+    }
+
+#if 0
+    /*
+     * It's not clear what to do with h_aliases.
+     *
+     * For names from the DNS it seems to contain the chain of CNAMEs,
+     * starting with the original qname from the question.  So for
+     * them we'd need to reply with a chain of:
+     *
+     *     h_aliases[i] CNAME h_aliases[i+1]
+     *
+     * OTOH, for the names from the hosts file it seems to contain all
+     * the names except the first one (which is considered primary and
+     * is reported as h_name).  In which case the reply should be:
+     *
+     *     h_aliases[i] CNAME h_name
+     *
+     * Obviously, we have no idea how the name was resolved, so we
+     * generate at most one CNAME for h_host (if differs) and ignore
+     * aliases altogehter.
+     */
+    for (i = 0; h->h_aliases[i] != NULL; ++i)
+    {
+        LogDbg(("NAT: hostres: ... %s\n", h->h_aliases[i]));
+    }
+#endif
+
+  out:
+    if (nanswers > 0)
+    {
+        int ok = m_append(pData, m, res->end - oend, (caddr_t)&res->buf[oend]);
+        if (!ok)
+        {
+            /* XXX: this may fail part way: restore old lenght, clear TC? */
+            return refuse(pData, m, RCode_ServFail);
+        }
+        pHdr->ancount = RT_H2N_U16(nanswers);
+    }
+    memcpy(mtod(m, char *), res->buf, sizeof(struct dnsmsg_header));
+    return m;
+}
+
+
+
+#define APPEND_PROLOGUE()                       \
+    ssize_t size = -1;                          \
+    size_t oend = res->end;                     \
+    ssize_t nbytes;                             \
+    do {} while (0)
+
+#define CHECKED(_append)                        \
+    do {                                        \
+        nbytes = (_append);                     \
+        if (RT_UNLIKELY(nbytes <= 0))           \
+        {                                       \
+            if (nbytes == 0)                    \
+                size = 0;                       \
+            goto out;                           \
+        }                                       \
+    } while (0)
+
+#define APPEND_EPILOGUE()                       \
+    do {                                        \
+        size = res->end - oend;                 \
+      out:                                      \
+        if (RT_UNLIKELY(size <= 0))             \
+            res->end = oend;                    \
+        return size;                            \
+    } while (0)
+
+
+/*
+ * A RR - rfc1035#section-3.4.1
+ */
+static ssize_t
+append_a(struct response *res, const char *name, struct in_addr addr)
+{
+    APPEND_PROLOGUE();
+
+    CHECKED( append_rrhdr(res, name, Type_A, 3600) );
+    CHECKED( append_u16(res, RT_H2N_U16_C(sizeof(addr))) );
+    CHECKED( append_u32(res, addr.s_addr) );
+ 
+    APPEND_EPILOGUE();
+}
+
+
+/*
+ * CNAME RR - rfc1035#section-3.3.1
+ */
+static ssize_t
+append_cname(struct response *res, const char *name, const char *cname)
+{
+    size_t rdlpos;
+    uint16_t rdlength;
+
+    APPEND_PROLOGUE();
+
+    CHECKED( append_rrhdr(res, name, Type_CNAME, 3600) );
+
+    rdlpos = res->end;
+    CHECKED( append_u16(res, 0) ); /* RDLENGTH placeholder */
+
+    CHECKED( append_name(res, cname) );
+
+    rdlength = RT_H2N_U16(nbytes);
+    memcpy(&res->buf[rdlpos], &rdlength, sizeof(rdlength));
+
+    APPEND_EPILOGUE();
+}
+
+
+/*
+ * Append common RR header, up to but not including RDLENGTH and RDATA
+ * proper (rfc1035#section-3.2.1).
+ */
+static ssize_t
+append_rrhdr(struct response *res, const char *name, uint16_t type, uint32_t ttl)
+{
+    APPEND_PROLOGUE();
+
+    CHECKED( append_name(res, name) );
+    CHECKED( append_u16(res, RT_H2N_U16(type)) );
+    CHECKED( append_u16(res, RT_H2N_U16_C(Class_IN)) );
+    CHECKED( append_u32(res, RT_H2N_U32(ttl)) );
+
+    APPEND_EPILOGUE();
+}
+
+
+static ssize_t
+append_name(struct response *res, const char *name)
+{
+    ssize_t size, nbytes;
+    struct label *root;
+    struct label *haystack, *needle;
+    struct label *head, **neck;
+    struct label *tail, **graft;
+    uint8_t *buf;
+    size_t wr, oend;
+    uint8_t terminator;
+    const char *s;
+
+    char namestr[DNS_MAX_NAME_LEN + 1];
+
+    size = -1;
+    oend = res->end;
+
+    /**
+     * Split new name into a list of labels encoding it into the
+     * temporary buffer.
+     */
+    root = NULL;
+
+    buf = RTMemAllocZ(strlen(name) + 1);
+    if (buf == NULL)
+        return -1;
+    wr = 0;
+
+    s = name;
+    while (*s != '\0') {
+        const char *part;
+        size_t poff, plen;
+        struct label *l;
+
+        part = s;
+        while (*s != '\0' && *s != '.')
+            ++s;
+
+        plen = s - part;
+
+        if (plen > DNS_MAX_LABEL_LEN)
+        {
+            LogErr(("NAT: hostres: name component too long\n"));
+            goto out;
+        }
+
+        if (*s == '.')
+        {
+            if (plen == 0)
+            {
+                LogErr(("NAT: hostres: empty name component\n"));
+                goto out;
+            }
+
+            ++s;
+        }
+        
+        poff = wr;
+
+        buf[poff] = (uint8_t)plen; /* length byte */
+        ++wr;
+
+        memcpy(&buf[wr], part, plen); /* label text */
+        wr += plen;
+
+        l = RTMemAllocZ(sizeof(*l));
+        if (l == NULL)
+            goto out;
+
+        l->buf = buf;
+        l->off = poff;
+        l->children = root;
+        root = l;
+    }
+
+
+    /**
+     * Search for a tail that is already encoded in the message.
+     */
+    neck = &root;               /* where needle head is connected */
+    needle = root;
+
+    tail = NULL;                /* tail in the haystack */
+    graft = &res->labels;
+    haystack = res->labels;
+
+    while (needle != NULL && haystack != NULL)
+    {
+        size_t nlen, hlen;
+
+        nlen = needle->buf[needle->off];
+        Assert((nlen & DNS_LABEL_PTR) == 0);
+
+        hlen = haystack->buf[haystack->off];
+        Assert((hlen & DNS_LABEL_PTR) == 0);
+
+        if (   nlen == hlen
+            && RTStrNICmp((char *)&needle->buf[needle->off+1],
+                          (char *)&haystack->buf[haystack->off+1],
+                          nlen) == 0)
+        {
+            neck = &needle->children;
+            needle = needle->children;
+
+            tail = haystack;
+            graft = &haystack->children;
+            haystack = haystack->children;
+        }
+        else
+        {
+            haystack = haystack->sibling;
+        }
+    }
+
+
+    /**
+     * Head contains (in reverse) the prefix that needs to be encoded
+     * and added to the haystack.  Tail points to existing suffix that
+     * can be compressed to a pointer into the haystack.
+     */
+    head = *neck;
+    if (head != NULL)
+    {
+        struct label *l;
+        size_t nlen, pfxlen, pfxdst;
+
+        nlen = needle->buf[head->off]; /* last component */
+        pfxlen = head->off + 1 + nlen; /* all prefix */
+        pfxdst = res->end;             /* in response buffer */
+
+        /* copy new prefix into response buffer */
+        nbytes = append_bytes(res, buf, pfxlen);
+        if (nbytes <= 0)
+        {
+            if (nbytes == 0)
+                size = 0;
+            goto out;
+        }
+
+        /* adjust labels to point to the response */
+        for (l = head; l != NULL; l = l->children)
+        {
+            l->buf = res->buf;
+            l->off += pfxdst;
+        }
+
+        *neck = NULL;           /* decapitate */
+
+        l = *graft;             /* graft to the labels tree */
+        *graft = head;
+        head->sibling = l;
+    }
+
+    if (tail == NULL)
+        nbytes = append_u8(res, 0);
+    else
+        nbytes = append_u16(res, RT_H2N_U16((DNS_LABEL_PTR << 8) | tail->off));
+    if (nbytes <= 0)
+    {
+        if (nbytes == 0)
+            size = 0;
+        goto out;
+    }
+
+    size = res->end - oend;
+  out:
+    if (RT_UNLIKELY(size <= 0))
+        res->end = oend;
+    free_labels(root);
+    RTMemFree(buf);
+    return size;
+}
+
+
+static ssize_t
+append_u32(struct response *res, uint32_t value)
+{
+    return append_bytes(res, (uint8_t *)&value, sizeof(value));
+}
+
+
+static ssize_t
+append_u16(struct response *res, uint16_t value)
+{
+    return append_bytes(res, (uint8_t *)&value, sizeof(value));
+}
+
+
+static ssize_t
+append_u8(struct response *res, uint8_t value)
+{
+    return append_bytes(res, &value, sizeof(value));
+}
+
+
+static ssize_t
+append_bytes(struct response *res, uint8_t *p, size_t size)
+{
+    if (check_space(res, size) == 0)
+        return 0;
+
+    memcpy(&res->buf[res->end], p, size);
+    res->end += size;
+    return size;
+}
+
+
+static ssize_t
+check_space(struct response *res, size_t size)
+{
+    if (   size > sizeof(res->buf)
+        || res->end > sizeof(res->buf) - size)
+        return 0;
+
+    return size;
+}
+
+
+/*
+ * Convert a chain of labels to a C string.
+ *
+ * I'd rather use a custom formatter for e.g. %R[label] , but it needs
+ * two arguments and microsoft VC doesn't support compound literals.
+ */
 static void
-doanswer(struct mbuf *m, struct hostent *pHostent)
-{
-    union dnsmsg_header *pHdr;
-    int i;
-
-    pHdr = mtod(m, union dnsmsg_header *);
-
-    if (!pHostent)
-    {
-        pHdr->X.qr = 1; /* response */
-        pHdr->X.aa = 1;
-        pHdr->X.rd = 1;
-        pHdr->X.rcode = 3;
+strnlabels(char *namebuf, size_t nbuflen, const uint8_t *msg, size_t off)
+{
+    size_t cb;
+    size_t llen;
+
+    namebuf[0] = '\0';
+    cb = 0;
+
+    llen = 0;
+
+    while (cb < nbuflen - 1) {
+        llen = msg[off];
+        if ((llen & DNS_LABEL_PTR) == DNS_LABEL_PTR)
+        {
+            off = ((llen & ~DNS_LABEL_PTR) << 8) | msg[off + 1];
+            llen = msg[off];
+        }
+
+        /* pointers to pointers should not happen */
+        if ((llen & DNS_LABEL_PTR) != 0)
+        {
+            cb += RTStrPrintf(namebuf + cb, nbuflen - cb, "[???]");
+            return;
+        }
+
+        if (llen == 0)
+        {
+            if (namebuf[0] == '\0')
+                cb += RTStrPrintf(namebuf + cb, nbuflen - cb, ".");
+            break;
+        }
+
+        if (namebuf[0] != '\0')
+            cb += RTStrPrintf(namebuf + cb, nbuflen - cb, ".");
+
+        cb += RTStrPrintf(namebuf + cb, nbuflen - cb,
+                          "%.*s", llen, (char *)&msg[off+1]);
+        off = off + 1 + llen;
+    }
+}
+
+
+static void
+LogLabelsTree(const char *before, struct label *l, const char *after)
+{
+    size_t llen;
+
+    if (before != NULL)
+        LogDbg(("%s", before));
+
+    if (l == NULL)
+    {
+        LogDbg(("NULL%s", after ? after : ""));
+        return;
+    }
+
+    if (l->children)
+        LogDbg(("("));
+
+    if (l->buf != NULL)
+    {
+        llen = l->buf[l->off];
+        if ((llen & DNS_LABEL_PTR) == 0)
+        {
+            LogDbg(("\"%.*s\"@%zu", llen, &l->buf[l->off+1], l->off));
+        }
+        else
+        {
+            LogDbg(("<invalid byte 0t%zu/0x%zf at offset %zd>",
+                    llen, llen, l->off));
+        }
     }
     else
     {
-        char *answers;
-        uint16_t off;
-        char **cstr;
-        char *c;
-        size_t anslen = 0;
-        uint16_t addr_off = (uint16_t)~0;
-        struct dns_meta_data *meta;
-
-        /* answers zone lays after query in response packet */
-        answers = (char *)pHdr + m->m_len;
-
-        off = (char *)&pHdr[1] - (char *)pHdr;
-        off |= (0x3 << 14);
-
-        /* add aliases */
-        for (cstr = pHostent->h_aliases; cstr && *cstr; cstr++)
-        {
-            uint16_t len;
-            struct dnsmsg_answer *ans = (struct dnsmsg_answer *)answers;
-            ans->name = htons(off);
-            ans->meta.type = htons(5); /* CNAME */
-            ans->meta.class = htons(1);
-            *(uint32_t *)ans->ttl = htonl(3600); /* 1h */
-            c = (addr_off == (uint16_t)~0 ? pHostent->h_name : *cstr);
-            len = strlen(c) + 2;
-            ans->rdata_len = htons(len);
-            ans->rdata[len - 1] = 0;
-            CStr2QStr(c, (char *)ans->rdata, len);
-            off = (char *)&ans->rdata - (char *)pHdr;
-            off |= (0x3 << 14);
-            if (addr_off == (uint16_t)~0)
-                addr_off = off;
-            answers = (char *)&ans[1] + len - 2;  /* note: 1 symbol already counted */
-            anslen += sizeof(struct dnsmsg_answer) + len - 2;
-            pHdr->X.ancount++;
-        }
-
-        /* add addresses */
-        for(i = 0; i < pHostent->h_length && pHostent->h_addr_list[i] != NULL; ++i)
-        {
-            struct dnsmsg_answer *ans = (struct dnsmsg_answer *)answers;
-
-            ans->name = htons(off);
-            ans->meta.type = htons(1);
-            ans->meta.class = htons(1);
-            *(uint32_t *)ans->ttl = htonl(3600); /* 1h */
-            ans->rdata_len = htons(4); /* IPv4 */
-            *(uint32_t *)ans->rdata = *(uint32_t *)pHostent->h_addr_list[i];
-            answers = (char *)&ans[1] + 2;
-            anslen += sizeof(struct dnsmsg_answer) + 3;
-            pHdr->X.ancount++;
-        }
-        pHdr->X.qr = 1; /* response */
-        pHdr->X.aa = 1;
-        pHdr->X.rd = 1;
-        pHdr->X.ra = 1;
-        pHdr->X.rcode = 0;
-        HTONS(pHdr->X.ancount);
-
-        m->m_len += anslen;
-    }
-}
-
-int
-hostresolver(PNATState pData, struct mbuf *m)
-{
-    int i;
-    /* Parse dns request */
-    char *qw_qname = NULL;
-    struct hostent *pHostent = NULL;
-    char pszCname[255];
-    int cname_len = 0;
-    struct dns_meta_data *meta;
-
-    union dnsmsg_header *pHdr = NULL;
-
-    pHdr = mtod(m, union dnsmsg_header *);
-
-    if (pHdr->X.qr == 1)
-        return 1; /* this is respose */
-
-    memset(pszCname, 0, sizeof(pszCname));
-    qw_qname = (char *)&pHdr[1];
-
-    if ((ntohs(pHdr->X.qdcount) != 1))
-    {
-        static bool fMultiWarn;
-        if (!fMultiWarn)
-        {
-            LogRel(("NAT: alias_dns: Multiple queries isn't supported\n"));
-            fMultiWarn = true;
-        }
-        return 1;
-    }
-
-    {
-        meta = (struct dns_meta_data *)(qw_qname + strlen(qw_qname) + 1);
-        Log(("pszQname:%s qtype:%hd qclass:%hd\n",
-            qw_qname, ntohs(meta->type), ntohs(meta->class)));
-
-        QStr2CStr(qw_qname, pszCname, sizeof(pszCname));
-        cname_len = RTStrNLen(pszCname, sizeof(pszCname));
-        /* Some guests like win-xp adds _dot_ after host name
-         * and after domain name (not passed with host resolver)
-         * that confuses host resolver.
-         */
-        if (   cname_len > 2
-            && pszCname[cname_len - 1] == '.'
-            && pszCname[cname_len - 2] == '.')
-        {
-            pszCname[cname_len - 1] = 0;
-            pszCname[cname_len - 2] = 0;
-        }
-        pHostent = gethostbyname(pszCname);
-#ifdef VBOX_WITH_DNSMAPPING_IN_HOSTRESOLVER
-        if (   pHostent
-            && !LIST_EMPTY(&pData->DNSMapHead))
-            alterHostentWithDataFromDNSMap(pData, pHostent);
-#endif
-        doanswer(m, pHostent);
-    }
-
-    return 0;
-}
-
-/*
- * qstr is z-string with -dot- replaced with \count to next -dot-
- * e.g. ya.ru is \02ya\02ru
- * Note: it's assumed that caller allocates buffer for cstr
- */
-static void QStr2CStr(const char *pcszQStr, char *pszStr, size_t cStr)
-{
-    const char *q;
-    char *c;
-    size_t cLen = 0;
-
-    Assert(cStr > 0);
-    for (q = pcszQStr, c = pszStr; *q != '\0' && cLen < cStr-1; q++, cLen++)
-    {
-        if (   isalpha(*q)
-            || isdigit(*q)
-            || *q == '-'
-            || *q == '_')
-        {
-           *c = *q;
-            c++;
-        }
-        else if (c != &pszStr[0])
-        {
-            *c = '.';
-            c++;
-        }
-    }
-    *c = '\0';
-}
-
-/*
- *
- */
-static void CStr2QStr(const char *pcszStr, char *pszQStr, size_t cQStr)
-{
-    const char *c;
-    const char *pc;
-    char *q;
-    size_t cLen = 0;
-
-    Assert(cQStr > 0);
-    for (c = pcszStr, q = pszQStr; *c != '\0' && cLen < cQStr-1; q++, cLen++)
-    {
-        /* at the begining or at -dot- position */
-        if (*c == '.' || (c == pcszStr && q == pszQStr))
-        {
-            if (c != pcszStr)
-                c++;
-            pc = strchr(c, '.');
-            *q = pc ? (pc - c) : strlen(c);
-        }
-        else
-        {
-            *q = *c;
-            c++;
-        }
-    }
-    *q = '\0';
+        LogDbg(("<*>"));
+    }
+
+    if (l->children)
+        LogLabelsTree(" ", l->children, ")");
+
+    if (l->sibling)
+        LogLabelsTree(" ", l->sibling, NULL);
+
+    if (after != NULL)
+        LogDbg(("%s", after));
+}
+
+
+static void
+free_labels(struct label *root)
+{
+    struct label TOP;    /* traverse the tree with pointer reversal */
+    struct label *b, *f;
+
+    if (root == NULL)
+        return;
+
+    RT_ZERO(TOP);
+
+    b = &TOP;
+    f = root;
+
+    while (f != &TOP) {
+        if (f->children) {      /* recurse left */
+            struct label *oldf = f;
+            struct label *newf = f->children;
+            oldf->children = b; /* reverse the pointer */
+            b = oldf;
+            f = newf;
+        }
+        else if (f->sibling) { /* turn right */
+            f->children = f->sibling;
+            f->sibling = NULL;
+        }
+        else {                  /* backtrack */
+            struct label *oldf = f; /* garbage */
+            struct label *oldb = b;
+            b = oldb->children;
+            oldb->children = NULL; /* oldf, but we are g/c'ing it */
+            f = oldb;
+
+            RTMemFree(oldf);
+        }
+    }
 }
 

trunk/src/VBox/Devices/Network/slirp/slirp.h

@@ -352 +352 @@
 
 /* hostres.c */
-int hostresolver(PNATState, struct mbuf *);
+struct mbuf *hostresolver(PNATState, struct mbuf *);
 
 /*slirp.c*/