1 files changed, 84 insertions, 8 deletions

diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index acdc4c989853..7f976af27bf0 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -1980,6 +1980,11 @@ static inline struct inet_timewait_sock *tw_next(struct inet_timewait_sock *tw)
                 hlist_nulls_entry(tw->tw_node.next, typeof(*tw), tw_node) : NULL;
 }
 
+/*
+ * Get next listener socket follow cur.  If cur is NULL, get first socket
+ * starting from bucket given in st->bucket; when st->bucket is zero the
+ * very first socket in the hash table is returned.
+ */
 static void *listening_get_next(struct seq_file *seq, void *cur)
 {
         struct inet_connection_sock *icsk;
@@ -1990,14 +1995,15 @@ static void *listening_get_next(struct seq_file *seq, void *cur)
         struct net *net = seq_file_net(seq);
 
         if (!sk) {
-                st->bucket = 0;
-                ilb = &tcp_hashinfo.listening_hash[0];
+                ilb = &tcp_hashinfo.listening_hash[st->bucket];
                 spin_lock_bh(&ilb->lock);
                 sk = sk_nulls_head(&ilb->head);
+                st->offset = 0;
                 goto get_sk;
         }
         ilb = &tcp_hashinfo.listening_hash[st->bucket];
         ++st->num;
+        ++st->offset;
 
         if (st->state == TCP_SEQ_STATE_OPENREQ) {
                 struct request_sock *req = cur;
@@ -2012,6 +2018,7 @@ static void *listening_get_next(struct seq_file *seq, void *cur)
                                 }
                                 req = req->dl_next;
                         }
+                        st->offset = 0;
                         if (++st->sbucket >= icsk->icsk_accept_queue.listen_opt->nr_table_entries)
                                 break;
 get_req:
@@ -2047,6 +2054,7 @@ start_req:
                 read_unlock_bh(&icsk->icsk_accept_queue.syn_wait_lock);
         }
         spin_unlock_bh(&ilb->lock);
+        st->offset = 0;
         if (++st->bucket < INET_LHTABLE_SIZE) {
                 ilb = &tcp_hashinfo.listening_hash[st->bucket];
                 spin_lock_bh(&ilb->lock);
@@ -2060,7 +2068,12 @@ out:
 
 static void *listening_get_idx(struct seq_file *seq, loff_t *pos)
 {
-        void *rc = listening_get_next(seq, NULL);
+        struct tcp_iter_state *st = seq->private;
+        void *rc;
+
+        st->bucket = 0;
+        st->offset = 0;
+        rc = listening_get_next(seq, NULL);
 
         while (rc && *pos) {
                 rc = listening_get_next(seq, rc);
@@ -2075,13 +2088,18 @@ static inline int empty_bucket(struct tcp_iter_state *st)
                 hlist_nulls_empty(&tcp_hashinfo.ehash[st->bucket].twchain);
 }
 
+/*
+ * Get first established socket starting from bucket given in st->bucket.
+ * If st->bucket is zero, the very first socket in the hash is returned.
+ */
 static void *established_get_first(struct seq_file *seq)
 {
         struct tcp_iter_state *st = seq->private;
         struct net *net = seq_file_net(seq);
         void *rc = NULL;
 
-        for (st->bucket = 0; st->bucket <= tcp_hashinfo.ehash_mask; ++st->bucket) {
+        st->offset = 0;
+        for (; st->bucket <= tcp_hashinfo.ehash_mask; ++st->bucket) {
                 struct sock *sk;
                 struct hlist_nulls_node *node;
                 struct inet_timewait_sock *tw;
@@ -2126,6 +2144,7 @@ static void *established_get_next(struct seq_file *seq, void *cur)
         struct net *net = seq_file_net(seq);
 
         ++st->num;
+        ++st->offset;
 
         if (st->state == TCP_SEQ_STATE_TIME_WAIT) {
                 tw = cur;
@@ -2142,6 +2161,7 @@ get_tw:
                 st->state = TCP_SEQ_STATE_ESTABLISHED;
 
                 /* Look for next non empty bucket */
+                st->offset = 0;
                 while (++st->bucket <= tcp_hashinfo.ehash_mask &&
                                 empty_bucket(st))
                         ;
@@ -2169,7 +2189,11 @@ out:
 
 static void *established_get_idx(struct seq_file *seq, loff_t pos)
 {
-        void *rc = established_get_first(seq);
+        struct tcp_iter_state *st = seq->private;
+        void *rc;
+
+        st->bucket = 0;
+        rc = established_get_first(seq);
 
         while (rc && pos) {
                 rc = established_get_next(seq, rc);
@@ -2194,24 +2218,72 @@ static void *tcp_get_idx(struct seq_file *seq, loff_t pos)
         return rc;
 }
 
+static void *tcp_seek_last_pos(struct seq_file *seq)
+{
+        struct tcp_iter_state *st = seq->private;
+        int offset = st->offset;
+        int orig_num = st->num;
+        void *rc = NULL;
+
+        switch (st->state) {
+        case TCP_SEQ_STATE_OPENREQ:
+        case TCP_SEQ_STATE_LISTENING:
+                if (st->bucket >= INET_LHTABLE_SIZE)
+                        break;
+                st->state = TCP_SEQ_STATE_LISTENING;
+                rc = listening_get_next(seq, NULL);
+                while (offset-- && rc)
+                        rc = listening_get_next(seq, rc);
+                if (rc)
+                        break;
+                st->bucket = 0;
+                /* Fallthrough */
+        case TCP_SEQ_STATE_ESTABLISHED:
+        case TCP_SEQ_STATE_TIME_WAIT:
+                st->state = TCP_SEQ_STATE_ESTABLISHED;
+                if (st->bucket > tcp_hashinfo.ehash_mask)
+                        break;
+                rc = established_get_first(seq);
+                while (offset-- && rc)
+                        rc = established_get_next(seq, rc);
+        }
+
+        st->num = orig_num;
+
+        return rc;
+}
+
 static void *tcp_seq_start(struct seq_file *seq, loff_t *pos)
 {
         struct tcp_iter_state *st = seq->private;
+        void *rc;
+
+        if (*pos && *pos == st->last_pos) {
+                rc = tcp_seek_last_pos(seq);
+                if (rc)
+                        goto out;
+        }
+
         st->state = TCP_SEQ_STATE_LISTENING;
         st->num = 0;
-        return *pos ? tcp_get_idx(seq, *pos - 1) : SEQ_START_TOKEN;
+        st->bucket = 0;
+        st->offset = 0;
+        rc = *pos ? tcp_get_idx(seq, *pos - 1) : SEQ_START_TOKEN;
+
+out:
+        st->last_pos = *pos;
+        return rc;
 }
 
 static void *tcp_seq_next(struct seq_file *seq, void *v, loff_t *pos)
 {
+        struct tcp_iter_state *st = seq->private;
         void *rc = NULL;
-        struct tcp_iter_state *st;
 
         if (v == SEQ_START_TOKEN) {
                 rc = tcp_get_idx(seq, 0);
                 goto out;
         }
-        st = seq->private;
 
         switch (st->state) {
         case TCP_SEQ_STATE_OPENREQ:
@@ -2219,6 +2291,8 @@ static void *tcp_seq_next(struct seq_file *seq, void *v, loff_t *pos)
                 rc = listening_get_next(seq, v);
                 if (!rc) {
                         st->state = TCP_SEQ_STATE_ESTABLISHED;
+                        st->bucket = 0;
+                        st->offset = 0;
                         rc        = established_get_first(seq);
                 }
                 break;
@@ -2229,6 +2303,7 @@ static void *tcp_seq_next(struct seq_file *seq, void *v, loff_t *pos)
         }
 out:
         ++*pos;
+        st->last_pos = *pos;
         return rc;
 }
 
@@ -2267,6 +2342,7 @@ static int tcp_seq_open(struct inode *inode, struct file *file)
 
         s = ((struct seq_file *)file->private_data)->private;
         s->family               = afinfo->family;
+        s->last_pos             = 0;
         return 0;
 }