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authorWillem de Bruijn <willemb@google.com>2021-01-09 17:18:33 -0500
committerJakub Kicinski <kuba@kernel.org>2021-01-11 18:20:09 -0800
commit97550f6fa59254435d864b92603de3ca4b5a99f8 (patch)
treea2236300b4b899a2e4a34e73dffe85910f455faa /include/linux
parent29766bcffad03da66892bef82674883e31f78fec (diff)
net: compound page support in skb_seq_read
skb_seq_read iterates over an skb, returning pointer and length of the next data range with each call. It relies on kmap_atomic to access highmem pages when needed. An skb frag may be backed by a compound page, but kmap_atomic maps only a single page. There are not enough kmap slots to always map all pages concurrently. Instead, if kmap_atomic is needed, iterate over each page. As this increases the number of calls, avoid this unless needed. The necessary condition is captured in skb_frag_must_loop. I tried to make the change as obvious as possible. It should be easy to verify that nothing changes if skb_frag_must_loop returns false. Tested: On an x86 platform with CONFIG_HIGHMEM=y CONFIG_DEBUG_KMAP_LOCAL_FORCE_MAP=y CONFIG_NETFILTER_XT_MATCH_STRING=y Run ip link set dev lo mtu 1500 iptables -A OUTPUT -m string --string 'badstring' -algo bm -j ACCEPT dd if=/dev/urandom of=in bs=1M count=20 nc -l -p 8000 > /dev/null & nc -w 1 -q 0 localhost 8000 < in Signed-off-by: Willem de Bruijn <willemb@google.com> Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Diffstat (limited to 'include/linux')
-rw-r--r--include/linux/skbuff.h1
1 files changed, 1 insertions, 0 deletions
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index c858adfb5a82..5f60c9e907c9 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -1203,6 +1203,7 @@ struct skb_seq_state {
struct sk_buff *root_skb;
struct sk_buff *cur_skb;
__u8 *frag_data;
+ __u32 frag_off;
};
void skb_prepare_seq_read(struct sk_buff *skb, unsigned int from,