netdev - [PATCH net-next 5/5] net: tso: add UDP segmentation support

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Date:   Wed, 17 Jun 2020 11:48:19 -0700
From:   Eric Dumazet <edumazet@...gle.com>
To:     "David S . Miller" <davem@...emloft.net>
Cc:     netdev <netdev@...r.kernel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Eric Dumazet <eric.dumazet@...il.com>,
        Willem de Bruijn <willemb@...gle.com>,
        Antoine Tenart <antoine.tenart@...tlin.com>
Subject: [PATCH net-next 5/5] net: tso: add UDP segmentation support

Note that like TCP, we do not support additional encapsulations,
and that checksums must be offloaded to the NIC.

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 net/core/tso.c | 29 ++++++++++++++++++-----------
 1 file changed, 18 insertions(+), 11 deletions(-)

diff --git a/net/core/tso.c b/net/core/tso.c
index 9f35518815bda275106d27bc5cc34b019429d254..4148f6d48953e1e1ebd878c3953f3e41d47832d9 100644
--- a/net/core/tso.c
+++ b/net/core/tso.c
@@ -16,7 +16,6 @@ EXPORT_SYMBOL(tso_count_descs);
 void tso_build_hdr(const struct sk_buff *skb, char *hdr, struct tso_t *tso,
 		   int size, bool is_last)
 {
-	struct tcphdr *tcph;
 	int hdr_len = skb_transport_offset(skb) + tso->tlen;
 	int mac_hdr_len = skb_network_offset(skb);
 
@@ -32,21 +31,29 @@ void tso_build_hdr(const struct sk_buff *skb, char *hdr, struct tso_t *tso,
 
 		iph->payload_len = htons(size + tso->tlen);
 	}
-	tcph = (struct tcphdr *)(hdr + skb_transport_offset(skb));
-	put_unaligned_be32(tso->tcp_seq, &tcph->seq);
+	hdr += skb_transport_offset(skb);
+	if (tso->tlen != sizeof(struct udphdr)) {
+		struct tcphdr *tcph = (struct tcphdr *)hdr;
 
-	if (!is_last) {
-		/* Clear all special flags for not last packet */
-		tcph->psh = 0;
-		tcph->fin = 0;
-		tcph->rst = 0;
+		put_unaligned_be32(tso->tcp_seq, &tcph->seq);
+
+		if (!is_last) {
+			/* Clear all special flags for not last packet */
+			tcph->psh = 0;
+			tcph->fin = 0;
+			tcph->rst = 0;
+		}
+	} else {
+		struct udphdr *uh = (struct udphdr *)hdr;
+
+		uh->len = htons(sizeof(*uh) + size);
 	}
 }
 EXPORT_SYMBOL(tso_build_hdr);
 
 void tso_build_data(const struct sk_buff *skb, struct tso_t *tso, int size)
 {
-	tso->tcp_seq += size;
+	tso->tcp_seq += size; /* not worth avoiding this operation for UDP */
 	tso->size -= size;
 	tso->data += size;
 
@@ -64,12 +71,12 @@ EXPORT_SYMBOL(tso_build_data);
 
 int tso_start(struct sk_buff *skb, struct tso_t *tso)
 {
-	int tlen = tcp_hdrlen(skb);
+	int tlen = skb_is_gso_tcp(skb) ? tcp_hdrlen(skb) : sizeof(struct udphdr);
 	int hdr_len = skb_transport_offset(skb) + tlen;
 
 	tso->tlen = tlen;
 	tso->ip_id = ntohs(ip_hdr(skb)->id);
-	tso->tcp_seq = ntohl(tcp_hdr(skb)->seq);
+	tso->tcp_seq = (tlen != sizeof(struct udphdr)) ? ntohl(tcp_hdr(skb)->seq) : 0;
 	tso->next_frag_idx = 0;
 	tso->ipv6 = vlan_get_protocol(skb) == htons(ETH_P_IPV6);
 
-- 
2.27.0.290.gba653c62da-goog