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Use getsockname to get source addresses.

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This was previously gotten by setting the source address to be the same
of the interface address of the matching route. However this can be
wrong; when making a normal socket connection the source address is
chosen differently. We create a SOCK_DGRAM socket, connect it, and read
the local address with getsockname.
This commit is contained in:
david
2011-06-27 18:05:39 +00:00
parent 4445ed7ed1
commit fd259a2422
1 changed files with 51 additions and 6 deletions
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57
libnetutil/netutil.cc
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@@ -3037,6 +3037,45 @@ static struct interface_info *find_loopback_iface(struct interface_info *ifaces,
return NULL;
}
/* Get the source address for routing to dst by creating a socket and asking the
operating system for the local address. */
static int get_srcaddr(const struct sockaddr_storage *dst,
struct sockaddr_storage *src)
{
static const unsigned short DUMMY_PORT = 1234;
struct sockaddr_storage dst_dummy;
socklen_t len;
int fd, rc;
fd = socket(dst->ss_family, SOCK_DGRAM, 0);
if (fd == -1)
netutil_fatal("%s: can't create socket: %s", __func__, socket_strerror(socket_errno()));
dst_dummy = *dst;
if (dst_dummy.ss_family == AF_INET) {
struct sockaddr_in *sin = (struct sockaddr_in *) &dst_dummy;
sin->sin_port = htons(DUMMY_PORT);
} else if (dst_dummy.ss_family == AF_INET6) {
struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *) &dst_dummy;
sin6->sin6_port = htons(DUMMY_PORT);
} else {
return -1;
}
rc = connect(fd, (struct sockaddr *) &dst_dummy, sizeof(struct sockaddr_in6));
if (rc == -1)
netutil_fatal("%s: can't connect socket: %s", __func__, socket_strerror(socket_errno()));
len = sizeof(*src);
rc = getsockname(fd, (struct sockaddr *) src, &len);
if (rc == -1)
netutil_fatal("%s: can't getsockname: %s", __func__, socket_strerror(socket_errno()));
close(fd);
return 0;
}
static int route_dst_generic(const struct sockaddr_storage *dst,
struct route_nfo *rnfo, const char *device,
const struct sockaddr_storage *spoofss) {
@@ -3093,8 +3132,10 @@ static int route_dst_generic(const struct sockaddr_storage *dst,
rnfo->ii = *loopback;
rnfo->direct_connect = 1;
/* But the source address we want to use is the target address. */
if (!spoofss)
rnfo->srcaddr = ifaces[i].addr;
if (!spoofss) {
if (get_srcaddr(dst, &rnfo->srcaddr) == -1)
return 0;
}
return 1;
}
@@ -3116,8 +3157,10 @@ static int route_dst_generic(const struct sockaddr_storage *dst,
rnfo->direct_connect = (sockaddr_equal_zero(&routes[i].gw) ||
sockaddr_equal(&routes[i].gw, &routes[i].device->addr) ||
sockaddr_equal(&routes[i].gw, dst));
if (!spoofss)
rnfo->srcaddr = routes[i].device->addr;
if (!spoofss) {
if (get_srcaddr(dst, &rnfo->srcaddr) == -1)
return 0;
}
rnfo->nexthop = routes[i].gw;
return 1;
@@ -3132,8 +3175,10 @@ static int route_dst_generic(const struct sockaddr_storage *dst,
rnfo->ii = ifaces[i];
rnfo->direct_connect = 1;
if (!spoofss)
rnfo->srcaddr = ifaces[i].addr;
if (!spoofss) {
if (get_srcaddr(dst, &rnfo->srcaddr) == -1)
return 0;
}
return 1;
}