[PATCH net-next 09/11] ip_gre: add drop reasons to the transmit path
From: Anton Danilov <hidden>
Date: 2026-08-31 21:52:08
Also in:
linux-kselftest, lkml
Subsystem:
networking [general], networking [ipv4/ipv6], the rest · Maintainers:
"David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, David Ahern, Ido Schimmel, Linus Torvalds
The five transmit functions of ip_gre collapse about twenty distinct failures into a plain kfree_skb() and a tx_dropped increment, which says nothing beyond "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 <redacted> --- 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 4d9bb6d186ae..c45e9590c94d 100644
--- a/net/ipv4/ip_gre.c
+++ b/net/ipv4/ip_gre.c@@ -511,23 +511,30 @@ static void gre_fb_xmit(struct sk_buff *skb, struct net_device *dev, IP_TUNNEL_DECLARE_FLAGS(flags) = { }; struct ip_tunnel_info *tun_info; const struct ip_tunnel_key *key; + enum skb_drop_reason reason = SKB_DROP_REASON_NOT_SPECIFIED; int tunnel_hlen; 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);
@@ -544,7 +551,7 @@ 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); }
@@ -554,6 +561,7 @@ static void erspan_fb_xmit(struct sk_buff *skb, struct net_device *dev) IP_TUNNEL_DECLARE_FLAGS(flags) = { }; struct ip_tunnel_info *tun_info; const struct ip_tunnel_key *key; + enum skb_drop_reason reason = SKB_DROP_REASON_NOT_SPECIFIED; struct erspan_metadata *md; bool truncate = false; __be16 proto;
@@ -563,29 +571,41 @@ 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; }
@@ -617,6 +637,7 @@ 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; }
@@ -629,7 +650,7 @@ 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); }
@@ -663,8 +684,10 @@ static netdev_tx_t ipgre_xmit(struct sk_buff *skb, struct ip_tunnel *tunnel = netdev_priv(dev); IP_TUNNEL_DECLARE_FLAGS(flags); const struct iphdr *tnl_params; + enum skb_drop_reason reason = SKB_DROP_REASON_NOT_SPECIFIED; - if (!pskb_inet_may_pull(skb)) + reason = pskb_inet_may_pull_reason(skb); + if (reason) goto free_skb; if (tunnel->collect_md) {
@@ -675,10 +698,13 @@ 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;
@@ -688,25 +714,31 @@ 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; }
@@ -716,10 +748,12 @@ static netdev_tx_t erspan_xmit(struct sk_buff *skb, { struct ip_tunnel *tunnel = netdev_priv(dev); IP_TUNNEL_DECLARE_FLAGS(flags); + enum skb_drop_reason reason = SKB_DROP_REASON_NOT_SPECIFIED; 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) {
@@ -727,15 +761,21 @@ 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; }
@@ -756,6 +796,7 @@ 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; }
@@ -764,7 +805,7 @@ 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; }
@@ -774,8 +815,10 @@ static netdev_tx_t gre_tap_xmit(struct sk_buff *skb, { struct ip_tunnel *tunnel = netdev_priv(dev); IP_TUNNEL_DECLARE_FLAGS(flags); + enum skb_drop_reason reason = SKB_DROP_REASON_NOT_SPECIFIED; - if (!pskb_inet_may_pull(skb)) + reason = pskb_inet_may_pull_reason(skb); + if (reason) goto free_skb; if (tunnel->collect_md) {
@@ -785,17 +828,21 @@ 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