[PATCH iproute2-next 2/4] lib: iplink: print warnings for missing data

[Edwin Peer]

The kernel might truncate VF info in IFLA_VFINFO_LIST. Sufficiently new
kernels will provide NLM_F_NEST_TRUNCATED in these cases, but this flag
has limited resolution, as it pertains to the entire netlink message. A
better approach is to compare the expected number of VFs in IFLA_NUM_VF
to how many were found in the list and warn accordingly.

Signed-off-by: Edwin Peer <edwin.p...@broadcom.com>
---
 ip/ipaddress.c   |  9 ++++++++-
 lib/libnetlink.c | 12 ++++++++++++
 2 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/ip/ipaddress.c b/ip/ipaddress.c
index 571346b15cc3..0bbcee2b3bb2 100644
--- a/ip/ipaddress.c
+++ b/ip/ipaddress.c
@@ -922,6 +922,7 @@ int print_linkinfo(struct nlmsghdr *n, void *arg)
        const char *name;
        unsigned int m_flag = 0;
        SPRINT_BUF(b1);
+       bool truncated_vfs = false;
 
        if (n->nlmsg_type != RTM_NEWLINK && n->nlmsg_type != RTM_DELLINK)
                return 0;
@@ -1199,15 +1200,18 @@ int print_linkinfo(struct nlmsghdr *n, void *arg)
 
        if ((do_link || show_details) && tb[IFLA_VFINFO_LIST] && 
tb[IFLA_NUM_VF]) {
                struct rtattr *i, *vflist = tb[IFLA_VFINFO_LIST];
-               int rem = RTA_PAYLOAD(vflist);
+               int rem = RTA_PAYLOAD(vflist), count = 0;
 
                open_json_array(PRINT_JSON, "vfinfo_list");
                for (i = RTA_DATA(vflist); RTA_OK(i, rem); i = RTA_NEXT(i, 
rem)) {
                        open_json_object(NULL);
                        print_vfinfo(fp, ifi, i);
                        close_json_object();
+                       count++;
                }
                close_json_array(PRINT_JSON, NULL);
+               if (count != rta_getattr_u32(tb[IFLA_NUM_VF]))
+                       truncated_vfs = true;
        }
 
        if (tb[IFLA_PROP_LIST]) {
@@ -1228,6 +1232,9 @@ int print_linkinfo(struct nlmsghdr *n, void *arg)
 
        print_string(PRINT_FP, NULL, "%s", "\n");
        fflush(fp);
+       /* prettier here if stderr and stdout go to the same place */
+       if (truncated_vfs)
+               fprintf(stderr, "Truncated VF list: %s\n", name);
        return 1;
 }
 
diff --git a/lib/libnetlink.c b/lib/libnetlink.c
index c958aa57d0cd..b1f07d4570cf 100644
--- a/lib/libnetlink.c
+++ b/lib/libnetlink.c
@@ -833,6 +833,9 @@ static int rtnl_dump_filter_l(struct rtnl_handle *rth,
                                if (h->nlmsg_flags & NLM_F_DUMP_INTR)
                                        dump_intr = 1;
 
+                               if (h->nlmsg_flags & NLM_F_NEST_TRUNCATED)
+                                       fprintf(stderr, "Incomplete data: 
truncated attribute list\n");
+
                                if (h->nlmsg_type == NLMSG_DONE) {
                                        err = rtnl_dump_done(h);
                                        if (err < 0) {
@@ -978,6 +981,9 @@ next:
                                continue;
                        }
 
+                       if (h->nlmsg_flags & NLM_F_NEST_TRUNCATED)
+                               fprintf(stderr, "Incomplete data: truncated 
attribute list\n");
+
                        if (h->nlmsg_type == NLMSG_ERROR) {
                                struct nlmsgerr *err = (struct nlmsgerr 
*)NLMSG_DATA(h);
                                int error = err->error;
@@ -1156,6 +1162,9 @@ int rtnl_listen(struct rtnl_handle *rtnl,
                                exit(1);
                        }
 
+                       if (h->nlmsg_flags & NLM_F_NEST_TRUNCATED)
+                               fprintf(stderr, "Incomplete data: truncated 
attribute list\n");
+
                        err = handler(&ctrl, h, jarg);
                        if (err < 0)
                                return err;
@@ -1206,6 +1215,9 @@ int rtnl_from_file(FILE *rtnl, rtnl_listen_filter_t 
handler,
                        return -1;
                }
 
+               if (h->nlmsg_flags & NLM_F_NEST_TRUNCATED)
+                       fprintf(stderr, "Incomplete data: truncated attribute 
list\n");
+
                status = fread(NLMSG_DATA(h), 1, NLMSG_ALIGN(l), rtnl);
 
                if (status != NLMSG_ALIGN(l)) {
-- 
2.30.0

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