ip: use rtnl_send_check() on flush commands, closes 6962

function                                             old     new   delta
rtnl_send_check                                        -     160    +160
xrtnl_wilddump_request                                64      66      +2
ipneigh_list_or_flush                                714     706      -8
rtnl_send                                             69       -     -69
------------------------------------------------------------------------------
(add/remove: 1/1 grow/shrink: 1/1 up/down: 162/-77)            Total: 85 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

5 files changed, 65 insertions, 17 deletions

diff --git a/networking/libiproute/ipaddress.c b/networking/libiproute/ipaddress.c
index fc6a4fb77..7b7e0154b 100644
--- a/networking/libiproute/ipaddress.c
+++ b/networking/libiproute/ipaddress.c
@@ -23,6 +23,7 @@
 
 struct filter_t {
         char *label;
+        /* Flush cmd buf. If !NULL, print_addrinfo() constructs flush commands in it */
         char *flushb;
         struct rtnl_handle *rth;
         int scope, scopemask;
@@ -34,6 +35,8 @@ struct filter_t {
         smallint showqueue;
         smallint oneline;
         smallint up;
+        /* Misnomer. Does not mean "flushed something" */
+        /* More like "flush commands were constructed by print_addrinfo()" */
         smallint flushed;
         inet_prefix pfx;
 } FIX_ALIASING;
@@ -201,7 +204,7 @@ static NOINLINE int print_linkinfo(const struct nlmsghdr *n)
 
 static int flush_update(void)
 {
-        if (rtnl_send(G_filter.rth, G_filter.flushb, G_filter.flushp) < 0) {
+        if (rtnl_send_check(G_filter.rth, G_filter.flushb, G_filter.flushp) < 0) {
                 bb_perror_msg("can't send flush request");
                 return -1;
         }
@@ -510,7 +513,6 @@ int FAST_FUNC ipaddr_list_or_flush(char **argv, int flush)
                 xrtnl_dump_filter(&rth, store_nlmsg, &ainfo);
         }
 
-
         if (G_filter.family && G_filter.family != AF_PACKET) {
                 struct nlmsg_list **lp;
                 lp = &linfo;
diff --git a/networking/libiproute/ipneigh.c b/networking/libiproute/ipneigh.c
index f572414e9..984dd4bdd 100644
--- a/networking/libiproute/ipneigh.c
+++ b/networking/libiproute/ipneigh.c
@@ -32,7 +32,10 @@ struct filter_t {
         int state;
         int unused_only;
         inet_prefix pfx;
+        /* Misnomer. Does not mean "flushed N something" */
+        /* More like "no_of_flush_commands_constructed_by_print_neigh()" */
         int flushed;
+        /* Flush cmd buf. If !NULL, print_neigh() constructs flush commands in it */
         char *flushb;
         int flushp;
         int flushe;
@@ -45,7 +48,7 @@ typedef struct filter_t filter_t;
 
 static int flush_update(void)
 {
-        if (rtnl_send(G_filter.rth, G_filter.flushb, G_filter.flushp) < 0) {
+        if (rtnl_send_check(G_filter.rth, G_filter.flushb, G_filter.flushp) < 0) {
                 bb_perror_msg("can't send flush request");
                 return -1;
         }
@@ -299,9 +302,7 @@ static int FAST_FUNC ipneigh_list_or_flush(char **argv, int flush)
                 G_filter.rth = &rth;
 
                 while (round < MAX_ROUNDS) {
-                        if (xrtnl_wilddump_request(&rth, G_filter.family, RTM_GETNEIGH) < 0) {
-                                bb_perror_msg_and_die("can't send dump request");
-                        }
+                        xrtnl_wilddump_request(&rth, G_filter.family, RTM_GETNEIGH);
                         G_filter.flushed = 0;
                         if (xrtnl_dump_filter(&rth, print_neigh, NULL) < 0) {
                                 bb_perror_msg_and_die("flush terminated");
diff --git a/networking/libiproute/iproute.c b/networking/libiproute/iproute.c
index 2a8610ea6..b11078ed5 100644
--- a/networking/libiproute/iproute.c
+++ b/networking/libiproute/iproute.c
@@ -26,7 +26,10 @@
 
 struct filter_t {
         int tb;
+        /* Misnomer. Does not mean "flushed something" */
+        /* More like "flush commands were constructed by print_route()" */
         smallint flushed;
+        /* Flush cmd buf. If !NULL, print_route() constructs flush commands in it */
         char *flushb;
         int flushp;
         int flushe;
@@ -53,7 +56,7 @@ typedef struct filter_t filter_t;
 
 static int flush_update(void)
 {
-        if (rtnl_send(G_filter.rth, G_filter.flushb, G_filter.flushp) < 0) {
+        if (rtnl_send_check(G_filter.rth, G_filter.flushb, G_filter.flushp) < 0) {
                 bb_perror_msg("can't send flush request");
                 return -1;
         }
diff --git a/networking/libiproute/libnetlink.c b/networking/libiproute/libnetlink.c
index 40955fcae..b0d4166ac 100644
--- a/networking/libiproute/libnetlink.c
+++ b/networking/libiproute/libnetlink.c
@@ -34,7 +34,7 @@ void FAST_FUNC xrtnl_open(struct rtnl_handle *rth/*, unsigned subscriptions*/)
         rth->seq = time(NULL);
 }
 
-int FAST_FUNC xrtnl_wilddump_request(struct rtnl_handle *rth, int family, int type)
+void FAST_FUNC xrtnl_wilddump_request(struct rtnl_handle *rth, int family, int type)
 {
         struct {
                 struct nlmsghdr nlh;
@@ -48,18 +48,45 @@ int FAST_FUNC xrtnl_wilddump_request(struct rtnl_handle *rth, int family, int ty
         req.nlh.nlmsg_seq = rth->dump = ++rth->seq;
         req.g.rtgen_family = family;
 
-        return rtnl_send(rth, (void*)&req, sizeof(req));
+        rtnl_send(rth, (void*)&req, sizeof(req));
 }
 
-//TODO: pass rth->fd instead of full rth?
-int FAST_FUNC rtnl_send(struct rtnl_handle *rth, char *buf, int len)
+/* A version which checks for e.g. EPERM errors.
+ * Try: setuidgid 1:1 ip addr flush dev eth0
+ */
+int FAST_FUNC rtnl_send_check(struct rtnl_handle *rth, const void *buf, int len)
 {
-        struct sockaddr_nl nladdr;
+        struct nlmsghdr *h;
+        int status;
+        char resp[1024];
 
-        memset(&nladdr, 0, sizeof(nladdr));
-        nladdr.nl_family = AF_NETLINK;
+        status = write(rth->fd, buf, len);
+        if (status < 0)
+                return status;
+
+        /* Check for immediate errors */
+        status = recv(rth->fd, resp, sizeof(resp), MSG_DONTWAIT|MSG_PEEK);
+        if (status < 0) {
+                if (errno == EAGAIN) /* if no error, this happens */
+                        return 0;
+                return -1;
+        }
 
-        return xsendto(rth->fd, buf, len, (struct sockaddr*)&nladdr, sizeof(nladdr));
+        for (h = (struct nlmsghdr *)resp;
+            NLMSG_OK(h, status);
+            h = NLMSG_NEXT(h, status)
+        ) {
+                if (h->nlmsg_type == NLMSG_ERROR) {
+                        struct nlmsgerr *err = (struct nlmsgerr*)NLMSG_DATA(h);
+                        if (h->nlmsg_len < NLMSG_LENGTH(sizeof(struct nlmsgerr)))
+                                bb_error_msg("ERROR truncated");
+                        else
+                                errno = -err->error;
+                        return -1;
+                }
+        }
+
+        return 0;
 }
 
 int FAST_FUNC rtnl_dump_request(struct rtnl_handle *rth, int type, void *req, int len)
diff --git a/networking/libiproute/libnetlink.h b/networking/libiproute/libnetlink.h
index 51bee2d67..1b082e019 100644
--- a/networking/libiproute/libnetlink.h
+++ b/networking/libiproute/libnetlink.h
@@ -20,7 +20,7 @@ struct rtnl_handle {
 
 extern void xrtnl_open(struct rtnl_handle *rth) FAST_FUNC;
 #define rtnl_close(rth) (close((rth)->fd))
-extern int xrtnl_wilddump_request(struct rtnl_handle *rth, int fam, int type) FAST_FUNC;
+extern void xrtnl_wilddump_request(struct rtnl_handle *rth, int fam, int type) FAST_FUNC;
 extern int rtnl_dump_request(struct rtnl_handle *rth, int type, void *req, int len) FAST_FUNC;
 extern int xrtnl_dump_filter(struct rtnl_handle *rth,
                 int (*filter)(const struct sockaddr_nl*, struct nlmsghdr *n, void*) FAST_FUNC,
@@ -34,8 +34,23 @@ extern int rtnl_talk(struct rtnl_handle *rtnl, struct nlmsghdr *n, pid_t peer,
                 int (*junk)(struct sockaddr_nl *,struct nlmsghdr *n, void *),
                 void *jarg) FAST_FUNC;
 
-extern int rtnl_send(struct rtnl_handle *rth, char *buf, int) FAST_FUNC;
+int rtnl_send_check(struct rtnl_handle *rth, const void *buf, int len) FAST_FUNC;
+//TODO: pass rth->fd instead of full rth?
+static ALWAYS_INLINE void rtnl_send(struct rtnl_handle *rth, const void *buf, int len)
+{
+        // Used to be:
+        //struct sockaddr_nl nladdr;
+        //memset(&nladdr, 0, sizeof(nladdr));
+        //nladdr.nl_family = AF_NETLINK;
+        //return xsendto(rth->fd, buf, len, (struct sockaddr*)&nladdr, sizeof(nladdr));
 
+        // iproute2-4.2.0 simplified the above to:
+        //return send(rth->fd, buf, len, 0);
+
+        // We are using even shorter:
+        xwrite(rth->fd, buf, len);
+        // and convert to void, inline.
+}
 
 extern int addattr32(struct nlmsghdr *n, int maxlen, int type, uint32_t data) FAST_FUNC;
 extern int addattr_l(struct nlmsghdr *n, int maxlen, int type, void *data, int alen) FAST_FUNC;