From f2696099c6c619aec4fe2b9691f0a81429957e65 Mon Sep 17 00:00:00 2001 From: Sean Tranchetti Date: Tue, 28 May 2019 12:22:54 -0600 Subject: [PATCH] udp: Avoid post-GRO UDP checksum recalculation Currently, when resegmenting an unexpected UDP GRO packet, the full UDP checksum will be calculated for every new SKB created by skb_segment() because the netdev features passed in by udp_rcv_segment() lack any information about checksum offload capabilities. Usually, we have no need to perform this calculation again, as 1) The GRO implementation guarantees that any packets making it to the udp_rcv_segment() function had correct checksums, and, more importantly, 2) Upon the successful return of udp_rcv_segment(), we immediately pull the UDP header off and either queue the segment to the socket or hand it off to a new protocol handler. Unless userspace has set the IP_CHECKSUM sockopt to indicate that they want the final checksum values, we can pass the needed netdev feature flags to __skb_gso_segment() to avoid checksumming each segment in skb_segment(). Fixes: cf329aa42b66 ("udp: cope with UDP GRO packet misdirection") Cc: Paolo Abeni Cc: Subash Abhinov Kasiviswanathan Signed-off-by: Sean Tranchetti Acked-by: Paolo Abeni Signed-off-by: David S. Miller --- include/net/udp.h | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/include/net/udp.h b/include/net/udp.h index d8ce937bc395..dbe030da20a1 100644 --- a/include/net/udp.h +++ b/include/net/udp.h @@ -471,12 +471,19 @@ void udpv6_encap_enable(void); static inline struct sk_buff *udp_rcv_segment(struct sock *sk, struct sk_buff *skb, bool ipv4) { + netdev_features_t features = NETIF_F_SG; struct sk_buff *segs; + /* Avoid csum recalculation by skb_segment unless userspace explicitly + * asks for the final checksum values + */ + if (!inet_get_convert_csum(sk)) + features |= NETIF_F_IP_CSUM | NETIF_F_IPV6_CSUM; + /* the GSO CB lays after the UDP one, no need to save and restore any * CB fragment */ - segs = __skb_gso_segment(skb, NETIF_F_SG, false); + segs = __skb_gso_segment(skb, features, false); if (unlikely(IS_ERR_OR_NULL(segs))) { int segs_nr = skb_shinfo(skb)->gso_segs;