From 21d52eabba00089e3319575616a429fb75309cb7 Mon Sep 17 00:00:00 2001
From: Thomas Graf <tgraf@suug.ch>
Date: Thu, 14 Jul 2011 10:51:49 +0200
Subject: Support for NLM_F_INTR

Check if a dump was interrupted and needs to be redone
---
 include/linux/netlink.h    |  1 +
 include/netlink/errno.h    |  3 ++-
 include/netlink/handlers.h |  2 ++
 lib/cache.c                | 14 ++++++++++++--
 lib/error.c                |  1 +
 lib/nl.c                   | 18 +++++++++++++++++-
 6 files changed, 35 insertions(+), 4 deletions(-)

diff --git a/include/linux/netlink.h b/include/linux/netlink.h
index 0abcdaf..3925254 100644
--- a/include/linux/netlink.h
+++ b/include/linux/netlink.h
@@ -49,6 +49,7 @@ struct nlmsghdr {
 #define NLM_F_MULTI		2	/* Multipart message, terminated by NLMSG_DONE */
 #define NLM_F_ACK		4	/* Reply with ack, with zero or error code */
 #define NLM_F_ECHO		8	/* Echo this request 		*/
+#define NLM_F_DUMP_INTR		16	/* Dump was inconsistent due to sequence change */
 
 /* Modifiers to GET request */
 #define NLM_F_ROOT	0x100	/* specify tree	root	*/
diff --git a/include/netlink/errno.h b/include/netlink/errno.h
index 267a745..f8b5130 100644
--- a/include/netlink/errno.h
+++ b/include/netlink/errno.h
@@ -49,8 +49,9 @@ extern "C" {
 #define NLE_PARSE_ERR		30
 #define NLE_NODEV		31
 #define NLE_IMMUTABLE		32
+#define NLE_DUMP_INTR		33
 
-#define NLE_MAX			NLE_IMMUTABLE
+#define NLE_MAX			NLE_DUMP_INTR
 
 extern const char *	nl_geterror(int);
 extern void		nl_perror(int, const char *);
diff --git a/include/netlink/handlers.h b/include/netlink/handlers.h
index f373f58..dfa2809 100644
--- a/include/netlink/handlers.h
+++ b/include/netlink/handlers.h
@@ -108,6 +108,8 @@ enum nl_cb_type {
 	NL_CB_SEQ_CHECK,
 	/** Sending of an acknowledge message has been requested */
 	NL_CB_SEND_ACK,
+	/** Flag NLM_F_DUMP_INTR is set in message */
+	NL_CB_DUMP_INTR,
 	__NL_CB_TYPE_MAX,
 };
 
diff --git a/lib/cache.c b/lib/cache.c
index 7afa42e..3b453a9 100644
--- a/lib/cache.c
+++ b/lib/cache.c
@@ -677,6 +677,7 @@ int nl_cache_resync(struct nl_sock *sk, struct nl_cache *cache,
 
 	NL_DBG(1, "Resyncing cache %p <%s>...\n", cache, nl_cache_name(cache));
 
+restart:
 	/* Mark all objects so we can see if some of them are obsolete */
 	nl_cache_mark_all(cache);
 
@@ -685,7 +686,9 @@ int nl_cache_resync(struct nl_sock *sk, struct nl_cache *cache,
 		goto errout;
 
 	err = __cache_pickup(sk, cache, &p);
-	if (err < 0)
+	if (err == -NLE_DUMP_INTR)
+		goto restart;
+	else if (err < 0)
 		goto errout;
 
 	nl_list_for_each_entry_safe(obj, next, &cache->c_items, ce_list) {
@@ -770,6 +773,7 @@ int nl_cache_refill(struct nl_sock *sk, struct nl_cache *cache)
 {
 	int err;
 
+restart:
 	err = nl_cache_request_full_dump(sk, cache);
 	if (err < 0)
 		return err;
@@ -778,7 +782,13 @@ int nl_cache_refill(struct nl_sock *sk, struct nl_cache *cache)
 	       cache, nl_cache_name(cache));
 	nl_cache_clear(cache);
 
-	return nl_cache_pickup(sk, cache);
+	err = nl_cache_pickup(sk, cache);
+	if (err == -NLE_DUMP_INTR) {
+		fprintf(stderr, "dump interrupted, restarting!\n");
+		goto restart;
+	}
+	
+	return err;
 }
 
 /** @} */
diff --git a/lib/error.c b/lib/error.c
index 8934020..e8ee474 100644
--- a/lib/error.c
+++ b/lib/error.c
@@ -46,6 +46,7 @@ static const char *errmsg[NLE_MAX+1] = {
 [NLE_PARSE_ERR]		= "Unable to parse object",
 [NLE_NODEV]		= "No such device",
 [NLE_IMMUTABLE]		= "Immutable attribute",
+[NLE_DUMP_INTR]		= "Dump inconsistency detected, interrupted",
 };
 
 /**
diff --git a/lib/nl.c b/lib/nl.c
index fc70374..cc450c7 100644
--- a/lib/nl.c
+++ b/lib/nl.c
@@ -559,7 +559,7 @@ do { \
 
 static int recvmsgs(struct nl_sock *sk, struct nl_cb *cb)
 {
-	int n, err = 0, multipart = 0;
+	int n, err = 0, multipart = 0, interrupted = 0;
 	unsigned char *buf = NULL;
 	struct nlmsghdr *hdr;
 	struct sockaddr_nl nla = {0};
@@ -631,6 +631,19 @@ continue_reading:
 
 		if (hdr->nlmsg_flags & NLM_F_MULTI)
 			multipart = 1;
+
+		if (hdr->nlmsg_flags & NLM_F_DUMP_INTR) {
+			if (cb->cb_set[NL_CB_DUMP_INTR])
+				NL_CB_CALL(cb, NL_CB_DUMP_INTR, msg);
+			else {
+				/*
+				 * We have to continue reading to clear
+				 * all messages until a NLMSG_DONE is
+				 * received and report the inconsistency.
+				 */
+				interrupted = 1;
+			}
+		}
 	
 		/* Other side wishes to see an ack for this message */
 		if (hdr->nlmsg_flags & NLM_F_ACK) {
@@ -738,6 +751,9 @@ out:
 	free(buf);
 	free(creds);
 
+	if (interrupted)
+		err = -NLE_DUMP_INTR;
+
 	return err;
 }
 
-- 
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