From: Anton Danilov <littlesmilingcloud@gmail.com>
To: netdev@vger.kernel.org
Cc: "David S . Miller" <davem@davemloft.net>,
Eric Dumazet <edumazet@google.com>,
Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
David Ahern <dsahern@kernel.org>, Simon Horman <horms@kernel.org>,
Ido Schimmel <idosch@nvidia.com>,
linux-kernel@vger.kernel.org
Subject: [PATCH net-next v4 08/10] ip_gre: add drop reasons to the transmit path
Date: Wed, 23 Sep 2026 01:15:05 +0300 [thread overview]
Message-ID: <20260922221507.3268127-9-littlesmilingcloud@gmail.com> (raw)
In-Reply-To: <20260922221507.3268127-1-littlesmilingcloud@gmail.com>
Each transmit function of ip_gre ends all of its failures in one
kfree_skb() and a tx_dropped increment, so a drop can be traced to the
function and to nothing more precise than "the tunnel did not send it".
No new reason is needed. The length helpers already compute one, so
pskb_inet_may_pull_reason() and pskb_may_pull_reason() are used instead
of their boolean wrappers, and the rest reuses:
- SKB_DROP_REASON_NOMEM for the headroom expansions, the offload
handling and the trims,
- SKB_DROP_REASON_TUNNEL_TXINFO for the collect_md paths, when the
metadata is missing or incomplete,
- SKB_DROP_REASON_UNHANDLED_PROTO for an ERSPAN version that is not
implemented,
- SKB_DROP_REASON_SKB_CSUM when the checksum starts before the data
the tunnel is about to send.
Assisted-by: Claude-Code:claude-opus-5
Signed-off-by: Anton Danilov <littlesmilingcloud@gmail.com>
---
net/ipv4/ip_gre.c | 101 +++++++++++++++++++++++++++++++++-------------
1 file changed, 74 insertions(+), 27 deletions(-)
diff --git a/net/ipv4/ip_gre.c b/net/ipv4/ip_gre.c
index e158d6e9d42a..ad669b3f8757 100644
--- a/net/ipv4/ip_gre.c
+++ b/net/ipv4/ip_gre.c
@@ -506,6 +506,7 @@ static int gre_handle_offloads(struct sk_buff *skb, bool csum)
static void gre_fb_xmit(struct sk_buff *skb, struct net_device *dev,
__be16 proto)
{
+ enum skb_drop_reason reason = SKB_DROP_REASON_NOT_SPECIFIED;
struct ip_tunnel *tunnel = netdev_priv(dev);
IP_TUNNEL_DECLARE_FLAGS(flags) = { };
struct ip_tunnel_info *tun_info;
@@ -514,19 +515,25 @@ static void gre_fb_xmit(struct sk_buff *skb, struct net_device *dev,
tun_info = skb_tunnel_info(skb);
if (unlikely(!tun_info || !(tun_info->mode & IP_TUNNEL_INFO_TX) ||
- ip_tunnel_info_af(tun_info) != AF_INET))
+ ip_tunnel_info_af(tun_info) != AF_INET)) {
+ reason = SKB_DROP_REASON_TUNNEL_TXINFO;
goto err_free_skb;
+ }
key = &tun_info->key;
tunnel_hlen = gre_calc_hlen(key->tun_flags);
- if (skb_cow_head(skb, dev->needed_headroom))
+ if (skb_cow_head(skb, dev->needed_headroom)) {
+ reason = SKB_DROP_REASON_NOMEM;
goto err_free_skb;
+ }
/* Push Tunnel header. */
if (gre_handle_offloads(skb, test_bit(IP_TUNNEL_CSUM_BIT,
- tunnel->parms.o_flags)))
+ tunnel->parms.o_flags))) {
+ reason = SKB_DROP_REASON_NOMEM;
goto err_free_skb;
+ }
__set_bit(IP_TUNNEL_CSUM_BIT, flags);
__set_bit(IP_TUNNEL_KEY_BIT, flags);
@@ -543,12 +550,13 @@ static void gre_fb_xmit(struct sk_buff *skb, struct net_device *dev,
return;
err_free_skb:
- kfree_skb(skb);
+ kfree_skb_reason(skb, reason);
DEV_STATS_INC(dev, tx_dropped);
}
static void erspan_fb_xmit(struct sk_buff *skb, struct net_device *dev)
{
+ enum skb_drop_reason reason = SKB_DROP_REASON_NOT_SPECIFIED;
struct ip_tunnel *tunnel = netdev_priv(dev);
IP_TUNNEL_DECLARE_FLAGS(flags) = { };
struct ip_tunnel_info *tun_info;
@@ -562,29 +570,41 @@ static void erspan_fb_xmit(struct sk_buff *skb, struct net_device *dev)
tun_info = skb_tunnel_info(skb);
if (unlikely(!tun_info || !(tun_info->mode & IP_TUNNEL_INFO_TX) ||
- ip_tunnel_info_af(tun_info) != AF_INET))
+ ip_tunnel_info_af(tun_info) != AF_INET)) {
+ reason = SKB_DROP_REASON_TUNNEL_TXINFO;
goto err_free_skb;
+ }
key = &tun_info->key;
- if (!test_bit(IP_TUNNEL_ERSPAN_OPT_BIT, tun_info->key.tun_flags))
+ if (!test_bit(IP_TUNNEL_ERSPAN_OPT_BIT, tun_info->key.tun_flags)) {
+ reason = SKB_DROP_REASON_TUNNEL_TXINFO;
goto err_free_skb;
- if (tun_info->options_len < sizeof(*md))
+ }
+ if (tun_info->options_len < sizeof(*md)) {
+ reason = SKB_DROP_REASON_TUNNEL_TXINFO;
goto err_free_skb;
+ }
md = ip_tunnel_info_opts(tun_info);
/* ERSPAN has fixed 8 byte GRE header */
version = md->version;
tunnel_hlen = 8 + erspan_hdr_len(version);
- if (skb_cow_head(skb, dev->needed_headroom))
+ if (skb_cow_head(skb, dev->needed_headroom)) {
+ reason = SKB_DROP_REASON_NOMEM;
goto err_free_skb;
+ }
- if (gre_handle_offloads(skb, false))
+ if (gre_handle_offloads(skb, false)) {
+ reason = SKB_DROP_REASON_NOMEM;
goto err_free_skb;
+ }
if (skb->len > dev->mtu + dev->hard_header_len) {
- if (pskb_trim(skb, dev->mtu + dev->hard_header_len))
+ if (pskb_trim(skb, dev->mtu + dev->hard_header_len)) {
+ reason = SKB_DROP_REASON_NOMEM;
goto err_free_skb;
+ }
truncate = true;
}
@@ -616,6 +636,7 @@ static void erspan_fb_xmit(struct sk_buff *skb, struct net_device *dev)
truncate, true);
proto = htons(ETH_P_ERSPAN2);
} else {
+ reason = SKB_DROP_REASON_UNHANDLED_PROTO;
goto err_free_skb;
}
@@ -628,7 +649,7 @@ static void erspan_fb_xmit(struct sk_buff *skb, struct net_device *dev)
return;
err_free_skb:
- kfree_skb(skb);
+ kfree_skb_reason(skb, reason);
DEV_STATS_INC(dev, tx_dropped);
}
@@ -659,11 +680,13 @@ static int gre_fill_metadata_dst(struct net_device *dev, struct sk_buff *skb)
static netdev_tx_t ipgre_xmit(struct sk_buff *skb,
struct net_device *dev)
{
+ enum skb_drop_reason reason = SKB_DROP_REASON_NOT_SPECIFIED;
struct ip_tunnel *tunnel = netdev_priv(dev);
IP_TUNNEL_DECLARE_FLAGS(flags);
const struct iphdr *tnl_params;
- if (!pskb_inet_may_pull(skb))
+ reason = pskb_inet_may_pull_reason(skb);
+ if (reason)
goto free_skb;
if (tunnel->collect_md) {
@@ -674,10 +697,13 @@ static netdev_tx_t ipgre_xmit(struct sk_buff *skb,
if (dev->header_ops) {
int pull_len = tunnel->hlen + sizeof(struct iphdr);
- if (skb_cow_head(skb, 0))
+ if (skb_cow_head(skb, 0)) {
+ reason = SKB_DROP_REASON_NOMEM;
goto free_skb;
+ }
- if (!pskb_may_pull(skb, pull_len))
+ reason = pskb_may_pull_reason(skb, pull_len);
+ if (reason)
goto free_skb;
tnl_params = (const struct iphdr *)skb->data;
@@ -687,25 +713,31 @@ static netdev_tx_t ipgre_xmit(struct sk_buff *skb,
skb_reset_mac_header(skb);
if (skb->ip_summed == CHECKSUM_PARTIAL &&
- skb_checksum_start(skb) < skb->data)
+ skb_checksum_start(skb) < skb->data) {
+ reason = SKB_DROP_REASON_SKB_CSUM;
goto free_skb;
+ }
} else {
- if (skb_cow_head(skb, dev->needed_headroom))
+ if (skb_cow_head(skb, dev->needed_headroom)) {
+ reason = SKB_DROP_REASON_NOMEM;
goto free_skb;
+ }
tnl_params = &tunnel->parms.iph;
}
ip_tunnel_flags_copy(flags, tunnel->parms.o_flags);
- if (gre_handle_offloads(skb, test_bit(IP_TUNNEL_CSUM_BIT, flags)))
+ if (gre_handle_offloads(skb, test_bit(IP_TUNNEL_CSUM_BIT, flags))) {
+ reason = SKB_DROP_REASON_NOMEM;
goto free_skb;
+ }
__gre_xmit(skb, dev, tnl_params, skb->protocol, flags);
return NETDEV_TX_OK;
free_skb:
- kfree_skb(skb);
+ kfree_skb_reason(skb, reason);
DEV_STATS_INC(dev, tx_dropped);
return NETDEV_TX_OK;
}
@@ -713,12 +745,14 @@ static netdev_tx_t ipgre_xmit(struct sk_buff *skb,
static netdev_tx_t erspan_xmit(struct sk_buff *skb,
struct net_device *dev)
{
+ enum skb_drop_reason reason = SKB_DROP_REASON_NOT_SPECIFIED;
struct ip_tunnel *tunnel = netdev_priv(dev);
IP_TUNNEL_DECLARE_FLAGS(flags);
bool truncate = false;
__be16 proto;
- if (!pskb_inet_may_pull(skb))
+ reason = pskb_inet_may_pull_reason(skb);
+ if (reason)
goto free_skb;
if (tunnel->collect_md) {
@@ -726,15 +760,21 @@ static netdev_tx_t erspan_xmit(struct sk_buff *skb,
return NETDEV_TX_OK;
}
- if (gre_handle_offloads(skb, false))
+ if (gre_handle_offloads(skb, false)) {
+ reason = SKB_DROP_REASON_NOMEM;
goto free_skb;
+ }
- if (skb_cow_head(skb, dev->needed_headroom))
+ if (skb_cow_head(skb, dev->needed_headroom)) {
+ reason = SKB_DROP_REASON_NOMEM;
goto free_skb;
+ }
if (skb->len > dev->mtu + dev->hard_header_len) {
- if (pskb_trim(skb, dev->mtu + dev->hard_header_len))
+ if (pskb_trim(skb, dev->mtu + dev->hard_header_len)) {
+ reason = SKB_DROP_REASON_NOMEM;
goto free_skb;
+ }
truncate = true;
}
@@ -755,6 +795,7 @@ static netdev_tx_t erspan_xmit(struct sk_buff *skb,
truncate, true);
proto = htons(ETH_P_ERSPAN2);
} else {
+ reason = SKB_DROP_REASON_UNHANDLED_PROTO;
goto free_skb;
}
@@ -763,7 +804,7 @@ static netdev_tx_t erspan_xmit(struct sk_buff *skb,
return NETDEV_TX_OK;
free_skb:
- kfree_skb(skb);
+ kfree_skb_reason(skb, reason);
DEV_STATS_INC(dev, tx_dropped);
return NETDEV_TX_OK;
}
@@ -771,10 +812,12 @@ static netdev_tx_t erspan_xmit(struct sk_buff *skb,
static netdev_tx_t gre_tap_xmit(struct sk_buff *skb,
struct net_device *dev)
{
+ enum skb_drop_reason reason = SKB_DROP_REASON_NOT_SPECIFIED;
struct ip_tunnel *tunnel = netdev_priv(dev);
IP_TUNNEL_DECLARE_FLAGS(flags);
- if (!pskb_inet_may_pull(skb))
+ reason = pskb_inet_may_pull_reason(skb);
+ if (reason)
goto free_skb;
if (tunnel->collect_md) {
@@ -784,17 +827,21 @@ static netdev_tx_t gre_tap_xmit(struct sk_buff *skb,
ip_tunnel_flags_copy(flags, tunnel->parms.o_flags);
- if (gre_handle_offloads(skb, test_bit(IP_TUNNEL_CSUM_BIT, flags)))
+ if (gre_handle_offloads(skb, test_bit(IP_TUNNEL_CSUM_BIT, flags))) {
+ reason = SKB_DROP_REASON_NOMEM;
goto free_skb;
+ }
- if (skb_cow_head(skb, dev->needed_headroom))
+ if (skb_cow_head(skb, dev->needed_headroom)) {
+ reason = SKB_DROP_REASON_NOMEM;
goto free_skb;
+ }
__gre_xmit(skb, dev, &tunnel->parms.iph, htons(ETH_P_TEB), flags);
return NETDEV_TX_OK;
free_skb:
- kfree_skb(skb);
+ kfree_skb_reason(skb, reason);
DEV_STATS_INC(dev, tx_dropped);
return NETDEV_TX_OK;
}
--
2.47.3
next prev parent reply other threads:[~2026-09-22 22:15 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-22 22:14 [PATCH net-next v4 00/10] tunnels: add core and gre drop reasons Anton Danilov
2026-09-22 22:14 ` [PATCH net-next v4 01/10] ip_tunnel: add drop reasons to the generic RX path Anton Danilov
2026-09-22 22:14 ` [PATCH net-next v4 02/10] ip6_tunnel: " Anton Danilov
2026-09-22 22:15 ` [PATCH net-next v4 03/10] gre: make gre_parse_header() report a drop reason Anton Danilov
2026-09-23 14:59 ` Ido Schimmel
2026-09-22 22:15 ` [PATCH net-next v4 04/10] ip_tunnel: add __iptunnel_pull_header_reason() Anton Danilov
2026-09-23 15:41 ` Ido Schimmel
2026-09-22 22:15 ` [PATCH net-next v4 05/10] ip_gre: add drop reasons to the RX path Anton Danilov
2026-09-22 22:15 ` [PATCH net-next v4 06/10] ip6_gre: " Anton Danilov
2026-09-22 22:15 ` [PATCH net-next v4 07/10] ip_tunnel: add drop reasons to the transmit path Anton Danilov
2026-09-23 15:53 ` Ido Schimmel
2026-09-22 22:15 ` Anton Danilov [this message]
2026-09-22 22:15 ` [PATCH net-next v4 09/10] ip6_gre: make prepare_ip6gre_xmit_other() void Anton Danilov
2026-09-22 22:15 ` [PATCH net-next v4 10/10] ip6_tunnel: add drop reasons to the transmit path Anton Danilov
2026-09-23 14:19 ` [PATCH net-next v4 00/10] tunnels: add core and gre drop reasons Ido Schimmel
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