From d9ef2e7bf99f59179b89d5c1c4d5b4919375daee Mon Sep 17 00:00:00 2001 From: Ihar Hrachyshka Date: Thu, 18 May 2017 12:41:20 -0700 Subject: [PATCH] arp: postpone addr_type calculation to as late as possible The addr_type retrieval can be costly, so it's worth trying to avoid its calculation as much as possible. This patch makes it calculated only for gratuitous ARP packets. This is especially important since later we may want to move is_garp calculation outside of arp_accept block, at which point the costly operation will be executed for all setups. The patch is the result of a discussion in net-dev: http://marc.info/?l=linux-netdev&m=149506354216994 Suggested-by: Julian Anastasov Signed-off-by: Ihar Hrachyshka Signed-off-by: David S. Miller --- net/ipv4/arp.c | 24 +++++++++++++++++------- 1 file changed, 17 insertions(+), 7 deletions(-) diff --git a/net/ipv4/arp.c b/net/ipv4/arp.c index ca6e1e6c1496..c22103cec823 100644 --- a/net/ipv4/arp.c +++ b/net/ipv4/arp.c @@ -641,12 +641,12 @@ void arp_xmit(struct sk_buff *skb) } EXPORT_SYMBOL(arp_xmit); -static bool arp_is_garp(struct net_device *dev, int addr_type, - __be16 ar_op, +static bool arp_is_garp(struct net *net, struct net_device *dev, + int *addr_type, __be16 ar_op, __be32 sip, __be32 tip, unsigned char *sha, unsigned char *tha) { - bool is_garp = tip == sip && addr_type == RTN_UNICAST; + bool is_garp = tip == sip; /* Gratuitous ARP _replies_ also require target hwaddr to be * the same as source. @@ -659,6 +659,11 @@ static bool arp_is_garp(struct net_device *dev, int addr_type, tha && !memcmp(tha, sha, dev->addr_len); + if (is_garp) { + *addr_type = inet_addr_type_dev_table(net, dev, sip); + if (*addr_type != RTN_UNICAST) + is_garp = false; + } return is_garp; } @@ -859,18 +864,23 @@ static int arp_process(struct net *net, struct sock *sk, struct sk_buff *skb) n = __neigh_lookup(&arp_tbl, &sip, dev, 0); if (IN_DEV_ARP_ACCEPT(in_dev)) { - unsigned int addr_type = inet_addr_type_dev_table(net, dev, sip); + addr_type = -1; /* Unsolicited ARP is not accepted by default. It is possible, that this option should be enabled for some devices (strip is candidate) */ - is_garp = arp_is_garp(dev, addr_type, arp->ar_op, + is_garp = arp_is_garp(net, dev, &addr_type, arp->ar_op, sip, tip, sha, tha); if (!n && - ((arp->ar_op == htons(ARPOP_REPLY) && - addr_type == RTN_UNICAST) || is_garp)) + (is_garp || + (arp->ar_op == htons(ARPOP_REPLY) && + (addr_type == RTN_UNICAST || + (addr_type < 0 && + /* postpone calculation to as late as possible */ + inet_addr_type_dev_table(net, dev, sip) == + RTN_UNICAST))))) n = __neigh_lookup(&arp_tbl, &sip, dev, 1); }