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netlink: Add nl_foreach_oftype to filter response message types

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In most cases where processing response messages, we expect only one type
of message (excepting NLMSG_DONE or NLMSG_ERROR), and so we need a test
and continue to skip anything else.  Add a helper macro to do this.
This also fixes a bug in nl_get_ext_if() where we didn't have such a test
and if we got a message other than RTM_NEWROUTE we would have parsed
its contents as nonsense.

Also add a warning message if we get such an unexpected message type, which
could be useful for debugging if we ever hit it.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
This commit is contained in:
David Gibson 2023-08-03 17:19:52 +10:00 committed by Stefano Brivio
parent 99ddd7ce83
commit a309318275
1 changed files with 14 additions and 15 deletions
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29
netlink.c
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@ -210,17 +210,25 @@ static struct nlmsghdr *nl_next(int s, char *buf, struct nlmsghdr *nh, ssize_t *
/**
* nl_foreach - 'for' type macro to step through netlink response messages
* nl_foreach_oftype - as above, but only messages of expected type
* @nh: Steps through each response header (struct nlmsghdr *)
* @status: When loop exits indicates if there was an error (ssize_t)
* @s: Netlink socket
* @buf: Buffer for responses (at least NLBUFSIZ long)
* @seq: Sequence number of request we're getting responses for
*/
* @type: Type of netlink message to process
*/
#define nl_foreach(nh, status, s, buf, seq) \
for ((nh) = nl_next((s), (buf), NULL, &(status)); \
((status) = nl_status((nh), (status), (seq))) > 0; \
(nh) = nl_next((s), (buf), (nh), &(status)))
#define nl_foreach_oftype(nh, status, s, buf, seq, type) \
nl_foreach((nh), (status), (s), (buf), (seq)) \
if ((nh)->nlmsg_type != (type)) { \
warn("netlink: Unexpected message type"); \
} else
/**
* nl_do() - Send netlink "do" request, and wait for acknowledgement
* @s: Netlink socket
@ -269,7 +277,7 @@ unsigned int nl_get_ext_if(int s, sa_family_t af)
size_t na;
seq = nl_send(s, &req, RTM_GETROUTE, NLM_F_DUMP, sizeof(req));
nl_foreach(nh, status, s, buf, seq) {
nl_foreach_oftype(nh, status, s, buf, seq, RTM_NEWROUTE) {
struct rtmsg *rtm = (struct rtmsg *)NLMSG_DATA(nh);
if (rtm->rtm_dst_len || rtm->rtm_family != af)
@ -321,14 +329,11 @@ void nl_route_get_def(int s, unsigned int ifi, sa_family_t af, void *gw)
uint16_t seq;
seq = nl_send(s, &req, RTM_GETROUTE, NLM_F_DUMP, sizeof(req));
nl_foreach(nh, status, s, buf, seq) {
nl_foreach_oftype(nh, status, s, buf, seq, RTM_NEWROUTE) {
struct rtmsg *rtm = (struct rtmsg *)NLMSG_DATA(nh);
struct rtattr *rta;
size_t na;
if (nh->nlmsg_type != RTM_NEWROUTE)
continue;
if (rtm->rtm_dst_len)
continue;
@ -518,14 +523,11 @@ void nl_addr_get(int s, unsigned int ifi, sa_family_t af,
uint16_t seq;
seq = nl_send(s, &req, RTM_GETADDR, NLM_F_DUMP, sizeof(req));
nl_foreach(nh, status, s, buf, seq) {
nl_foreach_oftype(nh, status, s, buf, seq, RTM_NEWADDR) {
struct ifaddrmsg *ifa = (struct ifaddrmsg *)NLMSG_DATA(nh);
struct rtattr *rta;
size_t na;
if (nh->nlmsg_type != RTM_NEWADDR)
continue;
if (ifa->ifa_index != ifi)
continue;
@ -639,7 +641,7 @@ void nl_addr_dup(int s_src, unsigned int ifi_src,
uint16_t seq;
seq = nl_send(s_src, &req, RTM_GETADDR, NLM_F_DUMP, sizeof(req));
nl_foreach(nh, status, s_src, buf, seq) {
nl_foreach_oftype(nh, status, s_src, buf, seq, RTM_NEWADDR) {
struct ifaddrmsg *ifa;
struct rtattr *rta;
size_t na;
@ -688,14 +690,11 @@ void nl_link_get_mac(int s, unsigned int ifi, void *mac)
uint16_t seq;
seq = nl_send(s, &req, RTM_GETLINK, 0, sizeof(req));
nl_foreach(nh, status, s, buf, seq) {
nl_foreach_oftype(nh, status, s, buf, seq, RTM_NEWLINK) {
struct ifinfomsg *ifm = (struct ifinfomsg *)NLMSG_DATA(nh);
struct rtattr *rta;
size_t na;
if (nh->nlmsg_type != RTM_NEWLINK)
continue;
for (rta = IFLA_RTA(ifm), na = RTM_PAYLOAD(nh);
RTA_OK(rta, na);
rta = RTA_NEXT(rta, na)) {