The original code which became rtnl_dump_done only shows netlink errors
if the protocol is NETLINK_SOCK_DIAG, but netlink dumps always appends
the length which contains any error encountered during the dump. Update
rtnl_dump_done to always show the error if there is one.
As an *example* without this patch, dumping a route object that exceeds
the internal buffer size terminates with no message to the user -- the
dump just ends because the NLMSG_DONE attribute was received. With this
patch the user at least gets a message that the dump was aborted.
$ ip ro ls
default via 10.0.2.2 dev eth0
10.0.2.0/24 dev eth0 proto kernel scope link src 10.0.2.15
10.10.0.0/16 dev veth1 proto kernel scope link src 10.10.0.1
172.16.1.0/24 dev br0.11 proto kernel scope link src 172.16.1.1
Error: Buffer too small for object
Dump terminated
The point of this patch is to notify the user of a failure versus
silently exiting on a partial dump. Because the NLMSG_DONE attribute
was received, the entire dump needs to be restarted to use a larger
buffer for EMSGSIZE errors. That could be done automatically but it
has other user impacts (e.g., duplicate output if the dump is
restarted) and should be the subject of a different patch.
Signed-off-by: David Ahern <dsah...@gmail.com>
---
lib/libnetlink.c | 28 +++++++++++++++++-----------
1 file changed, 17 insertions(+), 11 deletions(-)
diff --git a/lib/libnetlink.c b/lib/libnetlink.c
index 5b75b2db4e0b..d4b831f67ea2 100644
--- a/lib/libnetlink.c
+++ b/lib/libnetlink.c
@@ -266,21 +266,27 @@ static int rtnl_dump_done(const struct rtnl_handle *rth,
{
int len = *(int *)NLMSG_DATA(h);
- if (rth->proto == NETLINK_SOCK_DIAG) {
- if (h->nlmsg_len < NLMSG_LENGTH(sizeof(int))) {
- fprintf(stderr, "DONE truncated\n");
- return -1;
- }
-
+ if (h->nlmsg_len < NLMSG_LENGTH(sizeof(int))) {
+ fprintf(stderr, "DONE truncated\n");
+ return -1;
+ }
- if (len < 0) {
- errno = -len;
- if (errno == ENOENT || errno == EOPNOTSUPP)
- return -1;
+ if (len < 0) {
+ errno = -len;
+ switch (errno) {
+ case ENOENT:
+ case EOPNOTSUPP:
+ return -1;
+ case EMSGSIZE:
+ fprintf(stderr,
+ "Error: Buffer too small for object.\n");
+ break;
+ default:
perror("RTNETLINK answers");
- return len;
}
+ return len;
}
+
return 0;
}
--
2.11.0 (Apple Git-81)
