8 files changed, 106 insertions, 1 deletions

diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt
index ebc09a159f62..2b7cf19a06ad 100644
--- a/Documentation/networking/ip-sysctl.txt
+++ b/Documentation/networking/ip-sysctl.txt
@@ -46,6 +46,29 @@ ipfrag_secret_interval - INTEGER
         for the hash secret) for IP fragments.
         Default: 600
 
+ipfrag_max_dist - INTEGER
+        ipfrag_max_dist is a non-negative integer value which defines the 
+        maximum "disorder" which is allowed among fragments which share a 
+        common IP source address. Note that reordering of packets is 
+        not unusual, but if a large number of fragments arrive from a source 
+        IP address while a particular fragment queue remains incomplete, it 
+        probably indicates that one or more fragments belonging to that queue 
+        have been lost. When ipfrag_max_dist is positive, an additional check 
+        is done on fragments before they are added to a reassembly queue - if 
+        ipfrag_max_dist (or more) fragments have arrived from a particular IP 
+        address between additions to any IP fragment queue using that source 
+        address, it's presumed that one or more fragments in the queue are 
+        lost. The existing fragment queue will be dropped, and a new one 
+        started. An ipfrag_max_dist value of zero disables this check.
+
+        Using a very small value, e.g. 1 or 2, for ipfrag_max_dist can
+        result in unnecessarily dropping fragment queues when normal
+        reordering of packets occurs, which could lead to poor application 
+        performance. Using a very large value, e.g. 50000, increases the 
+        likelihood of incorrectly reassembling IP fragments that originate 
+        from different IP datagrams, which could result in data corruption.
+        Default: 64
+
 INET peer storage:
 
 inet_peer_threshold - INTEGER
diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h
index 4be34ef8c2f7..93fa765e47d3 100644
--- a/include/linux/sysctl.h
+++ b/include/linux/sysctl.h
@@ -390,6 +390,7 @@ enum
         NET_IPV4_ICMP_ERRORS_USE_INBOUND_IFADDR=109,
         NET_TCP_CONG_CONTROL=110,
         NET_TCP_ABC=111,
+        NET_IPV4_IPFRAG_MAX_DIST=112,
 };
 
 enum {
diff --git a/include/net/inetpeer.h b/include/net/inetpeer.h
index 7fda471002b6..0965515f40cf 100644
--- a/include/net/inetpeer.h
+++ b/include/net/inetpeer.h
@@ -25,6 +25,7 @@ struct inet_peer
         __u32                   v4daddr;        /* peer's address */
         __u16                   avl_height;
         __u16                   ip_id_count;    /* IP ID for the next packet */
+        atomic_t                rid;            /* Frag reception counter */
         __u32                   tcp_ts;
         unsigned long           tcp_ts_stamp;
 };
diff --git a/include/net/ip.h b/include/net/ip.h
index e4563bbee6ea..4d6294ba038e 100644
--- a/include/net/ip.h
+++ b/include/net/ip.h
@@ -45,6 +45,7 @@ struct inet_skb_parm
 #define IPSKB_TRANSLATED        2
 #define IPSKB_FORWARDED         4
 #define IPSKB_XFRM_TUNNEL_SIZE  8
+#define IPSKB_FRAG_COMPLETE     16
 };
 
 struct ipcm_cookie
@@ -168,6 +169,7 @@ extern int sysctl_ipfrag_high_thresh;
 extern int sysctl_ipfrag_low_thresh;
 extern int sysctl_ipfrag_time;
 extern int sysctl_ipfrag_secret_interval;
+extern int sysctl_ipfrag_max_dist;
 
 /* From inetpeer.c */
 extern int inet_peer_threshold;
diff --git a/net/ipv4/inetpeer.c b/net/ipv4/inetpeer.c
index 2fc3fd38924f..ce5fe3f74a3d 100644
--- a/net/ipv4/inetpeer.c
+++ b/net/ipv4/inetpeer.c
@@ -401,6 +401,7 @@ struct inet_peer *inet_getpeer(__u32 daddr, int create)
                 return NULL;
         n->v4daddr = daddr;
         atomic_set(&n->refcnt, 1);
+        atomic_set(&n->rid, 0);
         n->ip_id_count = secure_ip_id(daddr);
         n->tcp_ts_stamp = 0;
 
diff --git a/net/ipv4/ip_fragment.c b/net/ipv4/ip_fragment.c
index 8ce0ce2ee48e..ce2b70ce4018 100644
--- a/net/ipv4/ip_fragment.c
+++ b/net/ipv4/ip_fragment.c
@@ -22,6 +22,7 @@
  *              Patrick McHardy :       LRU queue of frag heads for evictor.
  */
 
+#include <linux/compiler.h>
 #include <linux/config.h>
 #include <linux/module.h>
 #include <linux/types.h>
@@ -38,6 +39,7 @@
 #include <net/ip.h>
 #include <net/icmp.h>
 #include <net/checksum.h>
+#include <net/inetpeer.h>
 #include <linux/tcp.h>
 #include <linux/udp.h>
 #include <linux/inet.h>
@@ -56,6 +58,8 @@
 int sysctl_ipfrag_high_thresh = 256*1024;
 int sysctl_ipfrag_low_thresh = 192*1024;
 
+int sysctl_ipfrag_max_dist = 64;
+
 /* Important NOTE! Fragment queue must be destroyed before MSL expires.
  * RFC791 is wrong proposing to prolongate timer each fragment arrival by TTL.
  */
@@ -89,8 +93,10 @@ struct ipq {
         spinlock_t      lock;
         atomic_t        refcnt;
         struct timer_list timer;        /* when will this queue expire?         */
-        int             iif;
         struct timeval  stamp;
+        int             iif;
+        unsigned int    rid;
+        struct inet_peer *peer;
 };
 
 /* Hash table. */
@@ -195,6 +201,9 @@ static void ip_frag_destroy(struct ipq *qp, int *work)
         BUG_TRAP(qp->last_in&COMPLETE);
         BUG_TRAP(del_timer(&qp->timer) == 0);
 
+        if (qp->peer)
+                inet_putpeer(qp->peer);
+
         /* Release all fragment data. */
         fp = qp->fragments;
         while (fp) {
@@ -353,6 +362,7 @@ static struct ipq *ip_frag_create(unsigned hash, struct iphdr *iph, u32 user)
         qp->meat = 0;
         qp->fragments = NULL;
         qp->iif = 0;
+        qp->peer = sysctl_ipfrag_max_dist ? inet_getpeer(iph->saddr, 1) : NULL;
 
         /* Initialize a timer for this entry. */
         init_timer(&qp->timer);
@@ -398,6 +408,56 @@ static inline struct ipq *ip_find(struct iphdr *iph, u32 user)
         return ip_frag_create(hash, iph, user);
 }
 
+/* Is the fragment too far ahead to be part of ipq? */
+static inline int ip_frag_too_far(struct ipq *qp)
+{
+        struct inet_peer *peer = qp->peer;
+        unsigned int max = sysctl_ipfrag_max_dist;
+        unsigned int start, end;
+
+        int rc;
+
+        if (!peer || !max)
+                return 0;
+
+        start = qp->rid;
+        end = atomic_inc_return(&peer->rid);
+        qp->rid = end;
+
+        rc = qp->fragments && (end - start) > max;
+
+        if (rc) {
+                IP_INC_STATS_BH(IPSTATS_MIB_REASMFAILS);
+        }
+
+        return rc;
+}
+
+static int ip_frag_reinit(struct ipq *qp)
+{
+        struct sk_buff *fp;
+
+        if (!mod_timer(&qp->timer, jiffies + sysctl_ipfrag_time)) {
+                atomic_inc(&qp->refcnt);
+                return -ETIMEDOUT;
+        }
+
+        fp = qp->fragments;
+        do {
+                struct sk_buff *xp = fp->next;
+                frag_kfree_skb(fp, NULL);
+                fp = xp;
+        } while (fp);
+
+        qp->last_in = 0;
+        qp->len = 0;
+        qp->meat = 0;
+        qp->fragments = NULL;
+        qp->iif = 0;
+
+        return 0;
+}
+
 /* Add new segment to existing queue. */
 static void ip_frag_queue(struct ipq *qp, struct sk_buff *skb)
 {
@@ -408,6 +468,12 @@ static void ip_frag_queue(struct ipq *qp, struct sk_buff *skb)
         if (qp->last_in & COMPLETE)
                 goto err;
 
+        if (!(IPCB(skb)->flags & IPSKB_FRAG_COMPLETE) &&
+            unlikely(ip_frag_too_far(qp)) && unlikely(ip_frag_reinit(qp))) {
+                ipq_kill(qp);
+                goto err;
+        }
+
         offset = ntohs(skb->nh.iph->frag_off);
         flags = offset & ~IP_OFFSET;
         offset &= IP_OFFSET;
diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
index eba64e2bd397..2a830de3a699 100644
--- a/net/ipv4/ip_output.c
+++ b/net/ipv4/ip_output.c
@@ -445,6 +445,7 @@ int ip_fragment(struct sk_buff *skb, int (*output)(struct sk_buff*))
 
         hlen = iph->ihl * 4;
         mtu = dst_mtu(&rt->u.dst) - hlen;       /* Size of data space */
+        IPCB(skb)->flags |= IPSKB_FRAG_COMPLETE;
 
         /* When frag_list is given, use it. First, check its validity:
          * some transformers could create wrong frag_list or break existing
diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c
index 01444a02b48b..dbf82955aabe 100644
--- a/net/ipv4/sysctl_net_ipv4.c
+++ b/net/ipv4/sysctl_net_ipv4.c
@@ -22,6 +22,7 @@
 extern int sysctl_ip_nonlocal_bind;
 
 #ifdef CONFIG_SYSCTL
+static int zero;
 static int tcp_retr1_max = 255; 
 static int ip_local_port_range_min[] = { 1, 1 };
 static int ip_local_port_range_max[] = { 65535, 65535 };
@@ -614,6 +615,15 @@ ctl_table ipv4_table[] = {
                 .strategy       = &sysctl_jiffies
         },
         {
+                .ctl_name       = NET_IPV4_IPFRAG_MAX_DIST,
+                .procname       = "ipfrag_max_dist",
+                .data           = &sysctl_ipfrag_max_dist,
+                .maxlen         = sizeof(int),
+                .mode           = 0644,
+                .proc_handler   = &proc_dointvec_minmax,
+                .extra1         = &zero
+        },
+        {
                 .ctl_name       = NET_TCP_NO_METRICS_SAVE,
                 .procname       = "tcp_no_metrics_save",
                 .data           = &sysctl_tcp_nometrics_save,