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Don't double-count RTA_LENGTH in netlink messages.

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For each rtattr we add to the netlink message, we were adding
RTA_LENGTH(rtattr->rta_len) to the length of the netlink message. But
rtattr->rta_len was already calculated as RTA_LENGTH of something, and
doing RTA_LENGTH twice made the length 4 bytes longer than it should be.
This caused a log in dmesg:
	netlink: 4 bytes leftover after parsing attributes.
or
	netlink: 8 bytes leftover after parsing attributes.
if there was an IPv6 scope ID (because that causes two rtattrs instead
of one).

The new code is consistent with the rtnetlink(3) man page, which does
	rta->rta_len = sizeof(unsigned int);
	req.n.nlmsg_len = NLMSG_ALIGN(req.n.nlmsg_len) + RTA_LENGTH(sizeof(unsigned int));
We do the equivalent
	rta->rta_len = sizeof(unsigned int);
	req.n.nlmsg_len = NLMSG_ALIGN(req.n.nlmsg_len) + rta->rta_len;
This commit is contained in:
david 2011-09-03 17:22:07 +00:00
parent 7205f00499
commit a13313ad2f
1 changed files with 2 additions and 2 deletions
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4
libnetutil/netutil.cc
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@ -2965,7 +2965,7 @@ static int route_dst_netlink(const struct sockaddr_storage *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) + RTA_LENGTH(rtattr->rta_len);
nlmsg->nlmsg_len = NLMSG_ALIGN(nlmsg->nlmsg_len) + rtattr->rta_len;
/* Specific interface (sin6_scope_id) requested? */
if (ifindex > 0) {
@ -2975,7 +2975,7 @@ static int route_dst_netlink(const struct sockaddr_storage *dst,
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) + RTA_LENGTH(rtattr->rta_len);
nlmsg->nlmsg_len = NLMSG_ALIGN(nlmsg->nlmsg_len) + rtattr->rta_len;
}
iov.iov_base = nlmsg;