From 2b16f048729bf35e6c28a40cbfad07239f9dcd90 Mon Sep 17 00:00:00 2001 From: Daniel Axtens <dja@axtens.net> Date: Wed, 31 Jan 2018 14:15:33 +1100 Subject: [PATCH] net: create skb_gso_validate_mac_len() If you take a GSO skb, and split it into packets, will the MAC length (L2 + L3 + L4 headers + payload) of those packets be small enough to fit within a given length? Move skb_gso_mac_seglen() to skbuff.h with other related functions like skb_gso_network_seglen() so we can use it, and then create skb_gso_validate_mac_len to do the full calculation. Signed-off-by: Daniel Axtens <dja@axtens.net> Signed-off-by: David S. Miller <davem@davemloft.net> [ Srivatsa: Removed all references to GSO_BY_FRAGS, as that feature is not available on 4.4 kernels. ] Signed-off-by: Srivatsa S. Bhat <srivatsa@csail.mit.edu> --- include/linux/skbuff.h | 16 +++++++++++++ net/core/skbuff.c | 63 +++++++++++++++++++++++++++++++++++++++----------- net/sched/sch_tbf.c | 10 -------- 3 files changed, 66 insertions(+), 23 deletions(-) diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h index a6da214..2a62725 100644 --- a/include/linux/skbuff.h +++ b/include/linux/skbuff.h @@ -2896,6 +2896,7 @@ void skb_split(struct sk_buff *skb, struct sk_buff *skb1, const u32 len); int skb_shift(struct sk_buff *tgt, struct sk_buff *skb, int shiftlen); void skb_scrub_packet(struct sk_buff *skb, bool xnet); unsigned int skb_gso_transport_seglen(const struct sk_buff *skb); +bool skb_gso_validate_mac_len(const struct sk_buff *skb, unsigned int len); struct sk_buff *skb_segment(struct sk_buff *skb, netdev_features_t features); struct sk_buff *skb_vlan_untag(struct sk_buff *skb); int skb_ensure_writable(struct sk_buff *skb, int write_len); @@ -3651,5 +3652,20 @@ static inline unsigned int skb_gso_network_seglen(const struct sk_buff *skb) return hdr_len + skb_gso_transport_seglen(skb); } +/** + * skb_gso_mac_seglen - Return length of individual segments of a gso packet + * + * @skb: GSO skb + * + * skb_gso_mac_seglen is used to determine the real size of the + * individual segments, including MAC/L2, Layer3 (IP, IPv6) and L4 + * headers (TCP/UDP). + */ +static inline unsigned int skb_gso_mac_seglen(const struct sk_buff *skb) +{ + unsigned int hdr_len = skb_transport_header(skb) - skb_mac_header(skb); + return hdr_len + skb_gso_transport_seglen(skb); +} + #endif /* __KERNEL__ */ #endif /* _LINUX_SKBUFF_H */ diff --git a/net/core/skbuff.c b/net/core/skbuff.c index 7d344259..3c42478 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -4292,6 +4292,46 @@ unsigned int skb_gso_transport_seglen(const struct sk_buff *skb) } EXPORT_SYMBOL_GPL(skb_gso_transport_seglen); +/** + * skb_gso_size_check - check the skb size + * + * There are a couple of instances where we have a GSO skb, and we + * want to determine what size it would be after it is segmented. + * + * We might want to check: + * - L3+L4+payload size (e.g. IP forwarding) + * - L2+L3+L4+payload size (e.g. sanity check before passing to driver) + * + * This is a helper to do that correctly. + * + * @seg_len: The segmented length (from skb_gso_*_seglen). + * + * @max_len: The maximum permissible length. + * + * Returns true if the segmented length <= max length. + */ +static inline bool skb_gso_size_check(const struct sk_buff *skb, + unsigned int seg_len, + unsigned int max_len) { + return seg_len <= max_len; +} + + +/** + * skb_gso_validate_mac_len - Will a split GSO skb fit in a given length? + * + * @skb: GSO skb + * @len: length to validate against + * + * skb_gso_validate_mac_len validates if a given skb will fit a wanted + * length once split, including L2, L3 and L4 headers and the payload. + */ +bool skb_gso_validate_mac_len(const struct sk_buff *skb, unsigned int len) +{ + return skb_gso_size_check(skb, skb_gso_mac_seglen(skb), len); +} +EXPORT_SYMBOL_GPL(skb_gso_validate_mac_len); + static struct sk_buff *skb_reorder_vlan_header(struct sk_buff *skb) { int mac_len; diff --git a/net/sched/sch_tbf.c b/net/sched/sch_tbf.c index c2fbde7..93d6a21 100644 --- a/net/sched/sch_tbf.c +++ b/net/sched/sch_tbf.c @@ -142,16 +142,6 @@ static u64 psched_ns_t2l(const struct psched_ratecfg *r, return len; } -/* - * Return length of individual segments of a gso packet, - * including all headers (MAC, IP, TCP/UDP) - */ -static unsigned int skb_gso_mac_seglen(const struct sk_buff *skb) -{ - unsigned int hdr_len = skb_transport_header(skb) - skb_mac_header(skb); - return hdr_len + skb_gso_transport_seglen(skb); -} - /* GSO packet is too big, segment it so that tbf can transmit * each segment in time */ -- 2.7.4