From: Alexander Lobakin alobakin@pm.me
[ Upstream commit 7ad18ff6449cbd6beb26b53128ddf56d2685aa93 ]
Commit 38ec4944b593 ("gro: ensure frag0 meets IP header alignment") did the right thing, but missed the fact that napi_gro_frags() logics calls for skb_gro_reset_offset() *before* pulling Ethernet header to the skb linear space. That said, the introduced check for frag0 address being aligned to 4 always fails for it as Ethernet header is obviously 14 bytes long, and in case with NET_IP_ALIGN its start is not aligned to 4.
Fix this by adding @nhoff argument to skb_gro_reset_offset() which tells if an IP header is placed right at the start of frag0 or not. This restores Fast GRO for napi_gro_frags() that became very slow after the mentioned commit, and preserves the introduced check to avoid silent unaligned accesses.
From v1 [0]:
- inline tiny skb_gro_reset_offset() to let the code be optimized more efficively (esp. for the !NET_IP_ALIGN case) (Eric); - pull in Reviewed-by from Eric.
[0] https://lore.kernel.org/netdev/20210418114200.5839-1-alobakin@pm.me
Fixes: 38ec4944b593 ("gro: ensure frag0 meets IP header alignment") Reviewed-by: Eric Dumazet edumazet@google.com Signed-off-by: Alexander Lobakin alobakin@pm.me Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Sasha Levin sashal@kernel.org --- net/core/dev.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/net/core/dev.c b/net/core/dev.c index 64f4c7ec729d..2f17a4ac82f0 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -5857,7 +5857,7 @@ static struct list_head *gro_list_prepare(struct napi_struct *napi, return head; }
-static void skb_gro_reset_offset(struct sk_buff *skb) +static inline void skb_gro_reset_offset(struct sk_buff *skb, u32 nhoff) { const struct skb_shared_info *pinfo = skb_shinfo(skb); const skb_frag_t *frag0 = &pinfo->frags[0]; @@ -5868,7 +5868,7 @@ static void skb_gro_reset_offset(struct sk_buff *skb)
if (!skb_headlen(skb) && pinfo->nr_frags && !PageHighMem(skb_frag_page(frag0)) && - (!NET_IP_ALIGN || !(skb_frag_off(frag0) & 3))) { + (!NET_IP_ALIGN || !((skb_frag_off(frag0) + nhoff) & 3))) { NAPI_GRO_CB(skb)->frag0 = skb_frag_address(frag0); NAPI_GRO_CB(skb)->frag0_len = min_t(unsigned int, skb_frag_size(frag0), @@ -6101,7 +6101,7 @@ gro_result_t napi_gro_receive(struct napi_struct *napi, struct sk_buff *skb) skb_mark_napi_id(skb, napi); trace_napi_gro_receive_entry(skb);
- skb_gro_reset_offset(skb); + skb_gro_reset_offset(skb, 0);
ret = napi_skb_finish(napi, skb, dev_gro_receive(napi, skb)); trace_napi_gro_receive_exit(ret); @@ -6194,7 +6194,7 @@ static struct sk_buff *napi_frags_skb(struct napi_struct *napi) napi->skb = NULL;
skb_reset_mac_header(skb); - skb_gro_reset_offset(skb); + skb_gro_reset_offset(skb, hlen);
if (unlikely(skb_gro_header_hard(skb, hlen))) { eth = skb_gro_header_slow(skb, hlen, 0);