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netlink: Add nl_do() helper for simple operations with error checking

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So far we never checked for errors reported on netlink operations via
NLMSG_ERROR messages.  This has led to several subtle and tricky to debug
situations which would have been obvious if we knew that certain netlink
operations had failed.

Introduce a nl_do() helper that performs netlink "do" operations (that is
making a single change without retreiving complex information) with much
more thorough error checking.  As well as returning an error code if we
get an NLMSG_ERROR message, we also check for unexpected behaviour in
several places.  That way if we've made a mistake in our assumptions about
how netlink works it should result in a clear error rather than some subtle
misbehaviour.

We update those calls to nl_req() that can use the new wrapper to do so.
We will extend those to better handle errors in future.  We don't touch
non-"do" operations for now, those are a bit trickier.

Link: https://bugs.passt.top/show_bug.cgi?id=60
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 17:19:49 +10:00 committed by Stefano Brivio
parent 282581ba84
commit 9d4ab98d53
1 changed files with 47 additions and 12 deletions
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59
netlink.c
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@ -148,6 +148,47 @@ static ssize_t nl_req(int s, char *buf, void *req,
return n;
}
/**
* nl_do() - Send netlink "do" request, and wait for acknowledgement
* @s: Netlink socket
* @req: Request (will fill netlink header)
* @type: Request type
* @flags: Extra request flags (NLM_F_REQUEST and NLM_F_ACK assumed)
* @len: Request length
*
* Return: 0 on success, negative error code on error
*/
static int nl_do(int s, void *req, uint16_t type, uint16_t flags, ssize_t len)
{
struct nlmsghdr *nh;
char buf[NLBUFSIZ];
uint16_t seq;
ssize_t n;
n = nl_req(s, buf, req, type, flags, len);
seq = ((struct nlmsghdr *)req)->nlmsg_seq;
for (nh = (struct nlmsghdr *)buf;
NLMSG_OK(nh, n); nh = NLMSG_NEXT(nh, n)) {
struct nlmsgerr *errmsg;
if (nh->nlmsg_seq != seq)
die("netlink: Unexpected response sequence number");
switch (nh->nlmsg_type) {
case NLMSG_DONE:
return 0;
case NLMSG_ERROR:
errmsg = (struct nlmsgerr *)NLMSG_DATA(nh);
return errmsg->error;
default:
warn("netlink: Unexpected response message");
}
}
die("netlink: Missing acknowledgement of request");
}
/**
* nl_get_ext_if() - Get interface index supporting IP version being probed
* @s: Netlink socket
@ -289,7 +330,6 @@ void nl_route_set_def(int s, unsigned int ifi, sa_family_t af, void *gw)
.rta.rta_len = RTA_LENGTH(sizeof(unsigned int)),
.ifi = ifi,
};
char buf[NLBUFSIZ];
ssize_t len;
if (af == AF_INET6) {
@ -316,7 +356,7 @@ void nl_route_set_def(int s, unsigned int ifi, sa_family_t af, void *gw)
req.set.r4.rta_gw.rta_len = rta_len;
}
nl_req(s, buf, &req, RTM_NEWROUTE, NLM_F_CREATE | NLM_F_EXCL, len);
nl_do(s, &req, RTM_NEWROUTE, NLM_F_CREATE | NLM_F_EXCL, len);
}
/**
@ -385,12 +425,11 @@ void nl_route_dup(int s_src, unsigned int ifi_src,
NLMSG_OK(nh, n) && nh->nlmsg_type != NLMSG_DONE;
nh = NLMSG_NEXT(nh, n)) {
uint16_t flags = nh->nlmsg_flags;
char resp[NLBUFSIZ];
if (nh->nlmsg_type != RTM_NEWROUTE)
continue;
nl_req(s_dst, resp, nh, RTM_NEWROUTE,
nl_do(s_dst, nh, RTM_NEWROUTE,
(flags & ~NLM_F_DUMP_FILTERED) | NLM_F_CREATE,
nh->nlmsg_len);
}
@ -489,7 +528,6 @@ void nl_addr_set(int s, unsigned int ifi, sa_family_t af,
.ifa.ifa_prefixlen = prefix_len,
.ifa.ifa_scope = RT_SCOPE_UNIVERSE,
};
char buf[NLBUFSIZ];
ssize_t len;
if (af == AF_INET6) {
@ -518,7 +556,7 @@ void nl_addr_set(int s, unsigned int ifi, sa_family_t af,
req.set.a4.rta_a.rta_type = IFA_ADDRESS;
}
nl_req(s, buf, &req, RTM_NEWADDR, NLM_F_CREATE | NLM_F_EXCL, len);
nl_do(s, &req, RTM_NEWADDR, NLM_F_CREATE | NLM_F_EXCL, len);
}
/**
@ -550,7 +588,6 @@ void nl_addr_dup(int s_src, unsigned int ifi_src,
NLMSG_OK(nh, n) && nh->nlmsg_type != NLMSG_DONE;
nh = NLMSG_NEXT(nh, n)) {
struct ifaddrmsg *ifa;
char resp[NLBUFSIZ];
struct rtattr *rta;
size_t na;
@ -571,7 +608,7 @@ void nl_addr_dup(int s_src, unsigned int ifi_src,
rta->rta_type = IFA_UNSPEC;
}
nl_req(s_dst, resp, nh, RTM_NEWADDR,
nl_do(s_dst, nh, RTM_NEWADDR,
(nh->nlmsg_flags & ~NLM_F_DUMP_FILTERED) | NLM_F_CREATE,
nh->nlmsg_len);
}
@ -639,11 +676,10 @@ void nl_link_set_mac(int s, unsigned int ifi, void *mac)
.rta.rta_type = IFLA_ADDRESS,
.rta.rta_len = RTA_LENGTH(ETH_ALEN),
};
char buf[NLBUFSIZ];
memcpy(req.mac, mac, ETH_ALEN);
nl_req(s, buf, &req, RTM_NEWLINK, 0, sizeof(req));
nl_do(s, &req, RTM_NEWLINK, 0, sizeof(req));
}
/**
@ -669,11 +705,10 @@ void nl_link_up(int s, unsigned int ifi, int mtu)
.mtu = mtu,
};
ssize_t len = sizeof(req);
char buf[NLBUFSIZ];
if (!mtu)
/* Shorten request to drop MTU attribute */
len = offsetof(struct req_t, rta);
nl_req(s, buf, &req, RTM_NEWLINK, 0, len);
nl_do(s, &req, RTM_NEWLINK, 0, len);
}