net:Add sysctl_max_skb_frags
Devices may have limits on the number of fragments in an skb they support.
Current codebase uses a constant as maximum for number of fragments one
skb can hold and use.
When enabling scatter/gather and running traffic with many small messages
the codebase uses the maximum number of fragments and may thereby violate
the max for certain devices.
The patch introduces a global variable as max number of fragments.
Signed-off-by: Hans Westgaard Ry <hans.westgaard.ry@oracle.com>
Reviewed-by: Håkon Bugge <haakon.bugge@oracle.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 11f935c..4ce9ff7 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -299,6 +299,7 @@
#else
#define MAX_SKB_FRAGS (65536/PAGE_SIZE + 1)
#endif
+extern int sysctl_max_skb_frags;
typedef struct skb_frag_struct skb_frag_t;
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index b2df375..5bf88f5 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -79,6 +79,8 @@
struct kmem_cache *skbuff_head_cache __read_mostly;
static struct kmem_cache *skbuff_fclone_cache __read_mostly;
+int sysctl_max_skb_frags __read_mostly = MAX_SKB_FRAGS;
+EXPORT_SYMBOL(sysctl_max_skb_frags);
/**
* skb_panic - private function for out-of-line support
diff --git a/net/core/sysctl_net_core.c b/net/core/sysctl_net_core.c
index 95b6139..a6beb7b 100644
--- a/net/core/sysctl_net_core.c
+++ b/net/core/sysctl_net_core.c
@@ -26,6 +26,7 @@
static int one = 1;
static int min_sndbuf = SOCK_MIN_SNDBUF;
static int min_rcvbuf = SOCK_MIN_RCVBUF;
+static int max_skb_frags = MAX_SKB_FRAGS;
static int net_msg_warn; /* Unused, but still a sysctl */
@@ -392,6 +393,15 @@
.mode = 0644,
.proc_handler = proc_dointvec
},
+ {
+ .procname = "max_skb_frags",
+ .data = &sysctl_max_skb_frags,
+ .maxlen = sizeof(int),
+ .mode = 0644,
+ .proc_handler = proc_dointvec_minmax,
+ .extra1 = &one,
+ .extra2 = &max_skb_frags,
+ },
{ }
};
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 19746b3..0c36ef4 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -940,7 +940,7 @@
i = skb_shinfo(skb)->nr_frags;
can_coalesce = skb_can_coalesce(skb, i, page, offset);
- if (!can_coalesce && i >= MAX_SKB_FRAGS) {
+ if (!can_coalesce && i >= sysctl_max_skb_frags) {
tcp_mark_push(tp, skb);
goto new_segment;
}
@@ -1213,7 +1213,7 @@
if (!skb_can_coalesce(skb, i, pfrag->page,
pfrag->offset)) {
- if (i == MAX_SKB_FRAGS || !sg) {
+ if (i == sysctl_max_skb_frags || !sg) {
tcp_mark_push(tp, skb);
goto new_segment;
}