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Factor out a add_rtattr_addr function to add a source or destination spec.

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This is used to restrict what routes the Netlink layer will return to
us.
This commit is contained in:
david
2012-09-11 18:39:40 +00:00
parent ba88cb4f5d
commit be636dacaf
1 changed files with 65 additions and 38 deletions
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103
libnetutil/netutil.cc
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@@ -2990,6 +2990,66 @@ static int set_sockaddr(struct sockaddr_storage *ss, int af, void *data) {
return 0;
}
/* Add rtattrs to a netlink message specifying a source or destination address.
rta_type must be RTA_SRC or RTA_DST. This function adds either 1 or 2
rtattrs: it always adds either an RTA_SRC or RTA_DST, depending on rta_type.
It also adds either RTA_IIF or RTA_OIF if the address family is AF_INET6 and
the sockaddr_in6 has a non-zero sin6_scope_id. */
static void add_rtattr_addr(struct nlmsghdr *nlmsg,
struct rtattr **rtattr, unsigned int *len,
unsigned char rta_type,
const struct sockaddr_storage *ss) {
struct rtmsg *rtmsg;
const void *addr;
size_t addrlen;
int ifindex;
assert(rta_type == RTA_SRC || rta_type == RTA_DST);
ifindex = 0;
if (ss->ss_family == AF_INET) {
addr = &((struct sockaddr_in *) ss)->sin_addr.s_addr;
addrlen = IP_ADDR_LEN;
} else if (ss->ss_family == AF_INET6) {
const struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *) ss;
addr = sin6->sin6_addr.s6_addr;
addrlen = IP6_ADDR_LEN;
ifindex = sin6->sin6_scope_id;
} else {
netutil_fatal("%s: unknown address family %d", __func__, ss->ss_family);
}
rtmsg = (struct rtmsg *) (nlmsg + 1);
if (rta_type == RTA_SRC)
rtmsg->rtm_src_len = addrlen * 8;
else
rtmsg->rtm_dst_len = addrlen * 8;
/* Add an rtattr for the address. */
(*rtattr)->rta_type = rta_type;
(*rtattr)->rta_len = RTA_LENGTH(addrlen);
assert(RTA_OK(*rtattr, *len));
memcpy(RTA_DATA(*rtattr), addr, addrlen);
nlmsg->nlmsg_len = NLMSG_ALIGN(nlmsg->nlmsg_len) + (*rtattr)->rta_len;
*rtattr = RTA_NEXT(*rtattr, len);
/* Specific interface (sin6_scope_id) requested? */
if (ifindex > 0) {
/* Add an rtattr for the interface. */
if (rta_type == RTA_SRC)
(*rtattr)->rta_type = RTA_IIF;
else
(*rtattr)->rta_type = RTA_OIF;
(*rtattr)->rta_len = RTA_LENGTH(sizeof(uint32_t));
assert(RTA_OK(*rtattr, *len));
*(uint32_t *) RTA_DATA(*rtattr) = ifindex;
nlmsg->nlmsg_len = NLMSG_ALIGN(nlmsg->nlmsg_len) + (*rtattr)->rta_len;
*rtattr = RTA_NEXT(*rtattr, len);
}
}
/* Does route_dst using the Linux-specific rtnetlink interface. See rtnetlink(3)
and rtnetlink(7). */
static int route_dst_netlink(const struct sockaddr_storage *dst,
@@ -3002,25 +3062,8 @@ static int route_dst_netlink(const struct sockaddr_storage *dst,
struct rtmsg *rtmsg;
struct rtattr *rtattr;
unsigned char buf[512];
const void *addr;
size_t addrlen;
int ifindex;
int fd, rc, len;
ifindex = 0;
if (dst->ss_family == AF_INET) {
addr = &((struct sockaddr_in *) dst)->sin_addr.s_addr;
addrlen = IP_ADDR_LEN;
} else if (dst->ss_family == AF_INET6) {
const struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *) dst;
addr = sin6->sin6_addr.s6_addr;
addrlen = IP6_ADDR_LEN;
ifindex = sin6->sin6_scope_id;
} else {
netutil_fatal("%s: unknown address family %d", __func__, dst->ss_family);
}
unsigned int len;
int fd, rc;
fd = socket(AF_NETLINK, SOCK_RAW, NETLINK_ROUTE);
if (fd == -1)
@@ -3044,28 +3087,12 @@ static int route_dst_netlink(const struct sockaddr_storage *dst,
rtmsg = (struct rtmsg *) (nlmsg + 1);
rtmsg->rtm_family = dst->ss_family;
rtmsg->rtm_dst_len = addrlen * 8;
rtattr = RTM_RTA(rtmsg);
len = sizeof(buf) - ((unsigned char *) rtattr - buf);
len = sizeof(buf) - ((unsigned char *) RTM_RTA(rtmsg) - buf);
/* Add an rtattr for destination address. */
rtattr->rta_type = RTA_DST;
rtattr->rta_len = RTA_LENGTH(addrlen);
assert(RTA_OK(rtattr, len));
memcpy(RTA_DATA(rtattr), addr, addrlen);
nlmsg->nlmsg_len = NLMSG_ALIGN(nlmsg->nlmsg_len) + rtattr->rta_len;
/* Specific interface (sin6_scope_id) requested? */
if (ifindex > 0) {
/* Add an rtattr for outgoing interface. */
rtattr = RTA_NEXT(rtattr, len);
rtattr->rta_type = RTA_OIF;
rtattr->rta_len = RTA_LENGTH(sizeof(uint32_t));
assert(RTA_OK(rtattr, len));
*(uint32_t *) RTA_DATA(rtattr) = ifindex;
nlmsg->nlmsg_len = NLMSG_ALIGN(nlmsg->nlmsg_len) + rtattr->rta_len;
}
/* Add rtattrs for destination address and interface. */
add_rtattr_addr(nlmsg, &rtattr, &len, RTA_DST, dst);
iov.iov_base = nlmsg;
iov.iov_len = nlmsg->nlmsg_len;