linux/net/ipv4/tcp_offload.c
Coco Li 5eddb24901 gro: add support of (hw)gro packets to gro stack
Current GRO stack only supports incoming packets containing
one frame/MSS.

This patch changes GRO to accept packets that are already GRO.

HW-GRO (aka RSC for some vendors) is very often limited in presence
of interleaved packets. Linux SW GRO stack can complete the job
and provide larger GRO packets, thus reducing rate of ACK packets
and cpu overhead.

This also means BIG TCP can still be used, even if HW-GRO/RSC was
able to cook ~64 KB GRO packets.

v2: fix logic in tcp_gro_receive()

    Only support TCP for the moment (Paolo)

Co-Developed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Coco Li <lixiaoyan@google.com>
Acked-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2022-10-03 12:38:34 +01:00

360 lines
8.6 KiB
C

// SPDX-License-Identifier: GPL-2.0-or-later
/*
* IPV4 GSO/GRO offload support
* Linux INET implementation
*
* TCPv4 GSO/GRO support
*/
#include <linux/indirect_call_wrapper.h>
#include <linux/skbuff.h>
#include <net/gro.h>
#include <net/tcp.h>
#include <net/protocol.h>
static void tcp_gso_tstamp(struct sk_buff *skb, unsigned int ts_seq,
unsigned int seq, unsigned int mss)
{
while (skb) {
if (before(ts_seq, seq + mss)) {
skb_shinfo(skb)->tx_flags |= SKBTX_SW_TSTAMP;
skb_shinfo(skb)->tskey = ts_seq;
return;
}
skb = skb->next;
seq += mss;
}
}
static struct sk_buff *tcp4_gso_segment(struct sk_buff *skb,
netdev_features_t features)
{
if (!(skb_shinfo(skb)->gso_type & SKB_GSO_TCPV4))
return ERR_PTR(-EINVAL);
if (!pskb_may_pull(skb, sizeof(struct tcphdr)))
return ERR_PTR(-EINVAL);
if (unlikely(skb->ip_summed != CHECKSUM_PARTIAL)) {
const struct iphdr *iph = ip_hdr(skb);
struct tcphdr *th = tcp_hdr(skb);
/* Set up checksum pseudo header, usually expect stack to
* have done this already.
*/
th->check = 0;
skb->ip_summed = CHECKSUM_PARTIAL;
__tcp_v4_send_check(skb, iph->saddr, iph->daddr);
}
return tcp_gso_segment(skb, features);
}
struct sk_buff *tcp_gso_segment(struct sk_buff *skb,
netdev_features_t features)
{
struct sk_buff *segs = ERR_PTR(-EINVAL);
unsigned int sum_truesize = 0;
struct tcphdr *th;
unsigned int thlen;
unsigned int seq;
__be32 delta;
unsigned int oldlen;
unsigned int mss;
struct sk_buff *gso_skb = skb;
__sum16 newcheck;
bool ooo_okay, copy_destructor;
th = tcp_hdr(skb);
thlen = th->doff * 4;
if (thlen < sizeof(*th))
goto out;
if (!pskb_may_pull(skb, thlen))
goto out;
oldlen = (u16)~skb->len;
__skb_pull(skb, thlen);
mss = skb_shinfo(skb)->gso_size;
if (unlikely(skb->len <= mss))
goto out;
if (skb_gso_ok(skb, features | NETIF_F_GSO_ROBUST)) {
/* Packet is from an untrusted source, reset gso_segs. */
skb_shinfo(skb)->gso_segs = DIV_ROUND_UP(skb->len, mss);
segs = NULL;
goto out;
}
copy_destructor = gso_skb->destructor == tcp_wfree;
ooo_okay = gso_skb->ooo_okay;
/* All segments but the first should have ooo_okay cleared */
skb->ooo_okay = 0;
segs = skb_segment(skb, features);
if (IS_ERR(segs))
goto out;
/* Only first segment might have ooo_okay set */
segs->ooo_okay = ooo_okay;
/* GSO partial and frag_list segmentation only requires splitting
* the frame into an MSS multiple and possibly a remainder, both
* cases return a GSO skb. So update the mss now.
*/
if (skb_is_gso(segs))
mss *= skb_shinfo(segs)->gso_segs;
delta = htonl(oldlen + (thlen + mss));
skb = segs;
th = tcp_hdr(skb);
seq = ntohl(th->seq);
if (unlikely(skb_shinfo(gso_skb)->tx_flags & SKBTX_SW_TSTAMP))
tcp_gso_tstamp(segs, skb_shinfo(gso_skb)->tskey, seq, mss);
newcheck = ~csum_fold((__force __wsum)((__force u32)th->check +
(__force u32)delta));
while (skb->next) {
th->fin = th->psh = 0;
th->check = newcheck;
if (skb->ip_summed == CHECKSUM_PARTIAL)
gso_reset_checksum(skb, ~th->check);
else
th->check = gso_make_checksum(skb, ~th->check);
seq += mss;
if (copy_destructor) {
skb->destructor = gso_skb->destructor;
skb->sk = gso_skb->sk;
sum_truesize += skb->truesize;
}
skb = skb->next;
th = tcp_hdr(skb);
th->seq = htonl(seq);
th->cwr = 0;
}
/* Following permits TCP Small Queues to work well with GSO :
* The callback to TCP stack will be called at the time last frag
* is freed at TX completion, and not right now when gso_skb
* is freed by GSO engine
*/
if (copy_destructor) {
int delta;
swap(gso_skb->sk, skb->sk);
swap(gso_skb->destructor, skb->destructor);
sum_truesize += skb->truesize;
delta = sum_truesize - gso_skb->truesize;
/* In some pathological cases, delta can be negative.
* We need to either use refcount_add() or refcount_sub_and_test()
*/
if (likely(delta >= 0))
refcount_add(delta, &skb->sk->sk_wmem_alloc);
else
WARN_ON_ONCE(refcount_sub_and_test(-delta, &skb->sk->sk_wmem_alloc));
}
delta = htonl(oldlen + (skb_tail_pointer(skb) -
skb_transport_header(skb)) +
skb->data_len);
th->check = ~csum_fold((__force __wsum)((__force u32)th->check +
(__force u32)delta));
if (skb->ip_summed == CHECKSUM_PARTIAL)
gso_reset_checksum(skb, ~th->check);
else
th->check = gso_make_checksum(skb, ~th->check);
out:
return segs;
}
struct sk_buff *tcp_gro_receive(struct list_head *head, struct sk_buff *skb)
{
struct sk_buff *pp = NULL;
struct sk_buff *p;
struct tcphdr *th;
struct tcphdr *th2;
unsigned int len;
unsigned int thlen;
__be32 flags;
unsigned int mss = 1;
unsigned int hlen;
unsigned int off;
int flush = 1;
int i;
off = skb_gro_offset(skb);
hlen = off + sizeof(*th);
th = skb_gro_header(skb, hlen, off);
if (unlikely(!th))
goto out;
thlen = th->doff * 4;
if (thlen < sizeof(*th))
goto out;
hlen = off + thlen;
if (skb_gro_header_hard(skb, hlen)) {
th = skb_gro_header_slow(skb, hlen, off);
if (unlikely(!th))
goto out;
}
skb_gro_pull(skb, thlen);
len = skb_gro_len(skb);
flags = tcp_flag_word(th);
list_for_each_entry(p, head, list) {
if (!NAPI_GRO_CB(p)->same_flow)
continue;
th2 = tcp_hdr(p);
if (*(u32 *)&th->source ^ *(u32 *)&th2->source) {
NAPI_GRO_CB(p)->same_flow = 0;
continue;
}
goto found;
}
p = NULL;
goto out_check_final;
found:
/* Include the IP ID check below from the inner most IP hdr */
flush = NAPI_GRO_CB(p)->flush;
flush |= (__force int)(flags & TCP_FLAG_CWR);
flush |= (__force int)((flags ^ tcp_flag_word(th2)) &
~(TCP_FLAG_CWR | TCP_FLAG_FIN | TCP_FLAG_PSH));
flush |= (__force int)(th->ack_seq ^ th2->ack_seq);
for (i = sizeof(*th); i < thlen; i += 4)
flush |= *(u32 *)((u8 *)th + i) ^
*(u32 *)((u8 *)th2 + i);
/* When we receive our second frame we can made a decision on if we
* continue this flow as an atomic flow with a fixed ID or if we use
* an incrementing ID.
*/
if (NAPI_GRO_CB(p)->flush_id != 1 ||
NAPI_GRO_CB(p)->count != 1 ||
!NAPI_GRO_CB(p)->is_atomic)
flush |= NAPI_GRO_CB(p)->flush_id;
else
NAPI_GRO_CB(p)->is_atomic = false;
mss = skb_shinfo(p)->gso_size;
/* If skb is a GRO packet, make sure its gso_size matches prior packet mss.
* If it is a single frame, do not aggregate it if its length
* is bigger than our mss.
*/
if (unlikely(skb_is_gso(skb)))
flush |= (mss != skb_shinfo(skb)->gso_size);
else
flush |= (len - 1) >= mss;
flush |= (ntohl(th2->seq) + skb_gro_len(p)) ^ ntohl(th->seq);
#ifdef CONFIG_TLS_DEVICE
flush |= p->decrypted ^ skb->decrypted;
#endif
if (flush || skb_gro_receive(p, skb)) {
mss = 1;
goto out_check_final;
}
tcp_flag_word(th2) |= flags & (TCP_FLAG_FIN | TCP_FLAG_PSH);
out_check_final:
/* Force a flush if last segment is smaller than mss. */
if (unlikely(skb_is_gso(skb)))
flush = len != NAPI_GRO_CB(skb)->count * skb_shinfo(skb)->gso_size;
else
flush = len < mss;
flush |= (__force int)(flags & (TCP_FLAG_URG | TCP_FLAG_PSH |
TCP_FLAG_RST | TCP_FLAG_SYN |
TCP_FLAG_FIN));
if (p && (!NAPI_GRO_CB(skb)->same_flow || flush))
pp = p;
out:
NAPI_GRO_CB(skb)->flush |= (flush != 0);
return pp;
}
int tcp_gro_complete(struct sk_buff *skb)
{
struct tcphdr *th = tcp_hdr(skb);
skb->csum_start = (unsigned char *)th - skb->head;
skb->csum_offset = offsetof(struct tcphdr, check);
skb->ip_summed = CHECKSUM_PARTIAL;
skb_shinfo(skb)->gso_segs = NAPI_GRO_CB(skb)->count;
if (th->cwr)
skb_shinfo(skb)->gso_type |= SKB_GSO_TCP_ECN;
if (skb->encapsulation)
skb->inner_transport_header = skb->transport_header;
return 0;
}
EXPORT_SYMBOL(tcp_gro_complete);
INDIRECT_CALLABLE_SCOPE
struct sk_buff *tcp4_gro_receive(struct list_head *head, struct sk_buff *skb)
{
/* Don't bother verifying checksum if we're going to flush anyway. */
if (!NAPI_GRO_CB(skb)->flush &&
skb_gro_checksum_validate(skb, IPPROTO_TCP,
inet_gro_compute_pseudo)) {
NAPI_GRO_CB(skb)->flush = 1;
return NULL;
}
return tcp_gro_receive(head, skb);
}
INDIRECT_CALLABLE_SCOPE int tcp4_gro_complete(struct sk_buff *skb, int thoff)
{
const struct iphdr *iph = ip_hdr(skb);
struct tcphdr *th = tcp_hdr(skb);
th->check = ~tcp_v4_check(skb->len - thoff, iph->saddr,
iph->daddr, 0);
skb_shinfo(skb)->gso_type |= SKB_GSO_TCPV4;
if (NAPI_GRO_CB(skb)->is_atomic)
skb_shinfo(skb)->gso_type |= SKB_GSO_TCP_FIXEDID;
return tcp_gro_complete(skb);
}
static const struct net_offload tcpv4_offload = {
.callbacks = {
.gso_segment = tcp4_gso_segment,
.gro_receive = tcp4_gro_receive,
.gro_complete = tcp4_gro_complete,
},
};
int __init tcpv4_offload_init(void)
{
return inet_add_offload(&tcpv4_offload, IPPROTO_TCP);
}