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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , David Ahern , Simon Horman , Ido Schimmel , linux-kernel@vger.kernel.org Subject: [PATCH net-next v3 7/9] ip_gre: add drop reasons to the transmit path Date: Wed, 16 Sep 2026 17:37:15 +0300 Message-ID: <20260916143717.1875082-8-littlesmilingcloud@gmail.com> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260916143717.1875082-1-littlesmilingcloud@gmail.com> References: <20260916143717.1875082-1-littlesmilingcloud@gmail.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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 --- 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 dc203937eb9f..373532e90dea 100644 --- a/net/ipv4/ip_gre.c +++ b/net/ipv4/ip_gre.c @@ -507,6 +507,7 @@ 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; @@ -515,19 +516,25 @@ 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); @@ -544,12 +551,13 @@ 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; @@ -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); } @@ -660,11 +681,13 @@ 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) { @@ -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; } @@ -714,12 +746,14 @@ 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) { @@ -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; } @@ -772,10 +813,12 @@ 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) { @@ -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