[3/5] slirp: Add dns6 resolution

Commit Message

Samuel Thibault March 28, 2016, 11:44 p.m. UTC

This makes get_dns_addr address family-agnostic, thus allowing to add the
IPv6 case.

Signed-off-by: Samuel Thibault <[e-mail]>
---
 slirp/ip6.h      |  9 +++++++
 slirp/libslirp.h |  1 +
 slirp/slirp.c    | 72 ++++++++++++++++++++++++++++++++++++++++----------------
 slirp/socket.c   |  4 ++--
 4 files changed, 64 insertions(+), 22 deletions(-)

Comments

Thomas Huth March 30, 2016, 9:32 a.m. UTC | #1

On 29.03.2016 01:44, Samuel Thibault wrote:
> This makes get_dns_addr address family-agnostic, thus allowing to add the
> IPv6 case.
> 
> Signed-off-by: Samuel Thibault <[e-mail]>
> ---
>  slirp/ip6.h      |  9 +++++++
>  slirp/libslirp.h |  1 +
>  slirp/slirp.c    | 72 ++++++++++++++++++++++++++++++++++++++++----------------
>  slirp/socket.c   |  4 ++--
>  4 files changed, 64 insertions(+), 22 deletions(-)
[...]
> diff --git a/slirp/slirp.c b/slirp/slirp.c
> index 2f0d3a3..3558b47 100644
> --- a/slirp/slirp.c
> +++ b/slirp/slirp.c
> @@ -45,7 +45,9 @@ static QTAILQ_HEAD(slirp_instances, Slirp) slirp_instances =
>      QTAILQ_HEAD_INITIALIZER(slirp_instances);
>  
>  static struct in_addr dns_addr;
> +static struct in6_addr dns6_addr;
>  static u_int dns_addr_time;
> +static u_int dns6_addr_time;
>  
>  #define TIMEOUT_FAST 2  /* milliseconds */
>  #define TIMEOUT_SLOW 499  /* milliseconds */
> @@ -99,6 +101,11 @@ int get_dns_addr(struct in_addr *pdns_addr)
>      return 0;
>  }
>  
> +int get_dns6_addr(struct in6_addr *pdns_addr6)
> +{
> +    return -1;
> +}
> +
>  static void winsock_cleanup(void)
>  {
>      WSACleanup();
> @@ -106,36 +113,40 @@ static void winsock_cleanup(void)
>  
>  #else
>  
> -static struct stat dns_addr_stat;
> -
> -static int get_dns_addr_cached(struct in_addr *pdns_addr)
> +static int get_dns_addr_cached(void *pdns_addr, void *cached_addr,
> +                               socklen_t addrlen,
> +                               struct stat *cached_stat, u_int *cached_time)
>  {
>      struct stat old_stat;
>      if ((curtime - dns_addr_time) < TIMEOUT_DEFAULT) {

Shouldn't that be "*cached_time" now instead of "dns_addr_time"? Or what
is this cached_time parameter now good for?

> -        *pdns_addr = dns_addr;
> +        memcpy(pdns_addr, cached_addr, addrlen);
>          return 0;
>      }
> -    old_stat = dns_addr_stat;
> -    if (stat("/etc/resolv.conf", &dns_addr_stat) != 0) {
> +    old_stat = *cached_stat;
> +    if (stat("/etc/resolv.conf", cached_stat) != 0) {
>          return -1;
>      }
> -    if ((dns_addr_stat.st_dev == old_stat.st_dev)
> -        && (dns_addr_stat.st_ino == old_stat.st_ino)
> -        && (dns_addr_stat.st_size == old_stat.st_size)
> -        && (dns_addr_stat.st_mtime == old_stat.st_mtime)) {
> -        *pdns_addr = dns_addr;
> +    if ((cached_stat->st_dev == old_stat.st_dev)
> +        && (cached_stat->st_ino == old_stat.st_ino)
> +        && (cached_stat->st_size == old_stat.st_size)
> +        && (cached_stat->st_mtime == old_stat.st_mtime)) {
> +        memcpy(pdns_addr, cached_addr, addrlen);
>          return 0;
>      }
>      return 1;
>  }
>  
> -static int get_dns_addr_resolv_conf(struct in_addr *pdns_addr)
> +static int get_dns_addr_resolv_conf(int af, void *pdns_addr, void *cached_addr,
> +                                    socklen_t addrlen, u_int *cached_time)
>  {
>      char buff[512];
>      char buff2[257];
>      FILE *f;
>      int found = 0;
> -    struct in_addr tmp_addr;
> +    void *tmp_addr = alloca(addrlen);
> +#ifdef DEBUG
> +    char s[INET6_ADDRSTRLEN];
> +#endif
>  
>      f = fopen("/etc/resolv.conf", "r");
>      if (!f)
> @@ -146,13 +157,14 @@ static int get_dns_addr_resolv_conf(struct in_addr *pdns_addr)
>  #endif
>      while (fgets(buff, 512, f) != NULL) {
>          if (sscanf(buff, "nameserver%*[ \t]%256s", buff2) == 1) {
> -            if (!inet_aton(buff2, &tmp_addr))
> +            if (!inet_pton(af, buff2, tmp_addr)) {
>                  continue;
> +            }
>              /* If it's the first one, set it to dns_addr */
>              if (!found) {
> -                *pdns_addr = tmp_addr;
> -                dns_addr = tmp_addr;
> -                dns_addr_time = curtime;
> +                memcpy(pdns_addr, tmp_addr, addrlen);
> +                memcpy(cached_addr, tmp_addr, addrlen);
> +                *cached_time = curtime;
>              }
>  #ifdef DEBUG
>              else
> @@ -166,7 +178,7 @@ static int get_dns_addr_resolv_conf(struct in_addr *pdns_addr)
>              }
>  #ifdef DEBUG
>              else

Maybe you could also add proper curly braces for this else-path now, and
then add the "char s[INET6_ADDRSTRLEN]" definition here instead ... that
way you don't need the separate "#ifdef DEBUG" at the beginning of this
function.

> -                fprintf(stderr, "%s", inet_ntoa(tmp_addr));
> +                fprintf(stderr, "%s", inet_ntop(af, tmp_addr, s, sizeof(s)));

While inet_ntoa never returns NULL, inet_ntop might return NULL on
errors. I think glibc fprintf will likely survive such a NULL pointer,
but it might still be better to check the return value and print
something else if the return value was NULL ?

>  #endif
>          }
>      }
> @@ -176,16 +188,36 @@ static int get_dns_addr_resolv_conf(struct in_addr *pdns_addr)
>      return 0;
>  }
>  
> +static struct stat dns_addr_stat;

You could also move this definition into the get_dns_addr() function.

>  int get_dns_addr(struct in_addr *pdns_addr)
>  {
>      if (dns_addr.s_addr != 0) {
>          int ret;
> -        ret = get_dns_addr_cached(pdns_addr);
> +        ret = get_dns_addr_cached(pdns_addr, &dns_addr, sizeof(dns_addr),
> +                                  &dns_addr_stat, &dns_addr_time);
> +        if (ret <= 0) {
> +            return ret;
> +        }
> +    }
> +    return get_dns_addr_resolv_conf(AF_INET, pdns_addr, &dns_addr,
> +                                    sizeof(dns_addr), &dns_addr_time);
> +}
> +
> +static struct stat dns6_addr_stat;

You could also move this definition into the get_dns6_addr() function.

> +int get_dns6_addr(struct in6_addr *pdns6_addr)
> +{
> +    if (!in6_zero(&dns6_addr)) {
> +        int ret;
> +        ret = get_dns_addr_cached(pdns6_addr, &dns6_addr, sizeof(dns6_addr),
> +                                  &dns6_addr_stat, &dns6_addr_time);
>          if (ret <= 0) {
>              return ret;
>          }
>      }
> -    return get_dns_addr_resolv_conf(pdns_addr);
> +    return get_dns_addr_resolv_conf(AF_INET6, pdns6_addr, &dns6_addr,
> +                                    sizeof(dns6_addr), &dns6_addr_time);
>  }

 Thomas

Patch

diff --git a/slirp/ip6.h b/slirp/ip6.h
index 8ddfa24..da23de6 100644
--- a/slirp/ip6.h
+++ b/slirp/ip6.h
@@ -26,6 +26,12 @@ 
                         0x00, 0x00, 0x00, 0x00,\
                         0x00, 0x00, 0x00, 0x02 } }
 
+#define ZERO_ADDR  { .s6_addr = \
+                        { 0x00, 0x00, 0x00, 0x00,\
+                        0x00, 0x00, 0x00, 0x00,\
+                        0x00, 0x00, 0x00, 0x00,\
+                        0x00, 0x00, 0x00, 0x00 } }
+
 static inline bool in6_equal(const struct in6_addr *a, const struct in6_addr *b)
 {
     return memcmp(a, b, sizeof(*a)) == 0;
@@ -84,6 +90,9 @@  static inline bool in6_equal_mach(const struct in6_addr *a,
 #define in6_solicitednode_multicast(a)\
     (in6_equal_net(a, &(struct in6_addr)SOLICITED_NODE_PREFIX, 104))
 
+#define in6_zero(a)\
+    (in6_equal(a, &(struct in6_addr)ZERO_ADDR))
+
 /* Compute emulated host MAC address from its ipv6 address */
 static inline void in6_compute_ethaddr(struct in6_addr ip,
                                        uint8_t eth[ETH_ALEN])
diff --git a/slirp/libslirp.h b/slirp/libslirp.h
index 127aa41..b0cfbc5 100644
--- a/slirp/libslirp.h
+++ b/slirp/libslirp.h
@@ -7,6 +7,7 @@  struct Slirp;
 typedef struct Slirp Slirp;
 
 int get_dns_addr(struct in_addr *pdns_addr);
+int get_dns6_addr(struct in6_addr *pdns6_addr);
 
 Slirp *slirp_init(int restricted, bool in_enabled, struct in_addr vnetwork,
                   struct in_addr vnetmask, struct in_addr vhost,
diff --git a/slirp/slirp.c b/slirp/slirp.c
index 2f0d3a3..3558b47 100644
--- a/slirp/slirp.c
+++ b/slirp/slirp.c
@@ -45,7 +45,9 @@  static QTAILQ_HEAD(slirp_instances, Slirp) slirp_instances =
     QTAILQ_HEAD_INITIALIZER(slirp_instances);
 
 static struct in_addr dns_addr;
+static struct in6_addr dns6_addr;
 static u_int dns_addr_time;
+static u_int dns6_addr_time;
 
 #define TIMEOUT_FAST 2  /* milliseconds */
 #define TIMEOUT_SLOW 499  /* milliseconds */
@@ -99,6 +101,11 @@  int get_dns_addr(struct in_addr *pdns_addr)
     return 0;
 }
 
+int get_dns6_addr(struct in6_addr *pdns_addr6)
+{
+    return -1;
+}
+
 static void winsock_cleanup(void)
 {
     WSACleanup();
@@ -106,36 +113,40 @@  static void winsock_cleanup(void)
 
 #else
 
-static struct stat dns_addr_stat;
-
-static int get_dns_addr_cached(struct in_addr *pdns_addr)
+static int get_dns_addr_cached(void *pdns_addr, void *cached_addr,
+                               socklen_t addrlen,
+                               struct stat *cached_stat, u_int *cached_time)
 {
     struct stat old_stat;
     if ((curtime - dns_addr_time) < TIMEOUT_DEFAULT) {
-        *pdns_addr = dns_addr;
+        memcpy(pdns_addr, cached_addr, addrlen);
         return 0;
     }
-    old_stat = dns_addr_stat;
-    if (stat("/etc/resolv.conf", &dns_addr_stat) != 0) {
+    old_stat = *cached_stat;
+    if (stat("/etc/resolv.conf", cached_stat) != 0) {
         return -1;
     }
-    if ((dns_addr_stat.st_dev == old_stat.st_dev)
-        && (dns_addr_stat.st_ino == old_stat.st_ino)
-        && (dns_addr_stat.st_size == old_stat.st_size)
-        && (dns_addr_stat.st_mtime == old_stat.st_mtime)) {
-        *pdns_addr = dns_addr;
+    if ((cached_stat->st_dev == old_stat.st_dev)
+        && (cached_stat->st_ino == old_stat.st_ino)
+        && (cached_stat->st_size == old_stat.st_size)
+        && (cached_stat->st_mtime == old_stat.st_mtime)) {
+        memcpy(pdns_addr, cached_addr, addrlen);
         return 0;
     }
     return 1;
 }
 
-static int get_dns_addr_resolv_conf(struct in_addr *pdns_addr)
+static int get_dns_addr_resolv_conf(int af, void *pdns_addr, void *cached_addr,
+                                    socklen_t addrlen, u_int *cached_time)
 {
     char buff[512];
     char buff2[257];
     FILE *f;
     int found = 0;
-    struct in_addr tmp_addr;
+    void *tmp_addr = alloca(addrlen);
+#ifdef DEBUG
+    char s[INET6_ADDRSTRLEN];
+#endif
 
     f = fopen("/etc/resolv.conf", "r");
     if (!f)
@@ -146,13 +157,14 @@  static int get_dns_addr_resolv_conf(struct in_addr *pdns_addr)
 #endif
     while (fgets(buff, 512, f) != NULL) {
         if (sscanf(buff, "nameserver%*[ \t]%256s", buff2) == 1) {
-            if (!inet_aton(buff2, &tmp_addr))
+            if (!inet_pton(af, buff2, tmp_addr)) {
                 continue;
+            }
             /* If it's the first one, set it to dns_addr */
             if (!found) {
-                *pdns_addr = tmp_addr;
-                dns_addr = tmp_addr;
-                dns_addr_time = curtime;
+                memcpy(pdns_addr, tmp_addr, addrlen);
+                memcpy(cached_addr, tmp_addr, addrlen);
+                *cached_time = curtime;
             }
 #ifdef DEBUG
             else
@@ -166,7 +178,7 @@  static int get_dns_addr_resolv_conf(struct in_addr *pdns_addr)
             }
 #ifdef DEBUG
             else
-                fprintf(stderr, "%s", inet_ntoa(tmp_addr));
+                fprintf(stderr, "%s", inet_ntop(af, tmp_addr, s, sizeof(s)));
 #endif
         }
     }
@@ -176,16 +188,36 @@  static int get_dns_addr_resolv_conf(struct in_addr *pdns_addr)
     return 0;
 }
 
+static struct stat dns_addr_stat;
+
 int get_dns_addr(struct in_addr *pdns_addr)
 {
     if (dns_addr.s_addr != 0) {
         int ret;
-        ret = get_dns_addr_cached(pdns_addr);
+        ret = get_dns_addr_cached(pdns_addr, &dns_addr, sizeof(dns_addr),
+                                  &dns_addr_stat, &dns_addr_time);
+        if (ret <= 0) {
+            return ret;
+        }
+    }
+    return get_dns_addr_resolv_conf(AF_INET, pdns_addr, &dns_addr,
+                                    sizeof(dns_addr), &dns_addr_time);
+}
+
+static struct stat dns6_addr_stat;
+
+int get_dns6_addr(struct in6_addr *pdns6_addr)
+{
+    if (!in6_zero(&dns6_addr)) {
+        int ret;
+        ret = get_dns_addr_cached(pdns6_addr, &dns6_addr, sizeof(dns6_addr),
+                                  &dns6_addr_stat, &dns6_addr_time);
         if (ret <= 0) {
             return ret;
         }
     }
-    return get_dns_addr_resolv_conf(pdns_addr);
+    return get_dns_addr_resolv_conf(AF_INET6, pdns6_addr, &dns6_addr,
+                                    sizeof(dns6_addr), &dns6_addr_time);
 }
 
 #endif
diff --git a/slirp/socket.c b/slirp/socket.c
index b836c42..653257d 100644
--- a/slirp/socket.c
+++ b/slirp/socket.c
@@ -796,9 +796,9 @@  void sotranslate_out(struct socket *so, struct sockaddr_storage *addr)
         if (in6_equal_net(&so->so_faddr6, &slirp->vprefix_addr6,
                     slirp->vprefix_len)) {
             if (in6_equal(&so->so_faddr6, &slirp->vnameserver_addr6)) {
-                /*if (get_dns_addr(&addr) < 0) {*/ /* TODO */
+                if (get_dns6_addr(&sin6->sin6_addr) < 0) {
                     sin6->sin6_addr = in6addr_loopback;
-                /*}*/
+                }
             } else {
                 sin6->sin6_addr = in6addr_loopback;
             }