From 736013292e3ca5ec2aabb32daf72a73b1256ac57 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Wed, 7 Jun 2023 21:41:13 +0000 Subject: [PATCH] tcp: let tcp_mtu_probe() build headless packets tcp_mtu_probe() is still copying payload from skbs in the write queue, using skb_copy_bits(), ignoring potential errors. Modern TCP stack wants to only deal with payload found in page frags, as this is a prereq for TCPDirect (host stack might not have access to the payload) Signed-off-by: Eric Dumazet Link: https://lore.kernel.org/r/20230607214113.1992947-1-edumazet@google.com Signed-off-by: Jakub Kicinski --- net/ipv4/tcp_output.c | 60 +++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 58 insertions(+), 2 deletions(-) diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index cfe128b81a01..f8ce77ce7c3e 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -2319,6 +2319,57 @@ static bool tcp_can_coalesce_send_queue_head(struct sock *sk, int len) return true; } +static int tcp_clone_payload(struct sock *sk, struct sk_buff *to, + int probe_size) +{ + skb_frag_t *lastfrag = NULL, *fragto = skb_shinfo(to)->frags; + int i, todo, len = 0, nr_frags = 0; + const struct sk_buff *skb; + + if (!sk_wmem_schedule(sk, to->truesize + probe_size)) + return -ENOMEM; + + skb_queue_walk(&sk->sk_write_queue, skb) { + const skb_frag_t *fragfrom = skb_shinfo(skb)->frags; + + if (skb_headlen(skb)) + return -EINVAL; + + for (i = 0; i < skb_shinfo(skb)->nr_frags; i++, fragfrom++) { + if (len >= probe_size) + goto commit; + todo = min_t(int, skb_frag_size(fragfrom), + probe_size - len); + len += todo; + if (lastfrag && + skb_frag_page(fragfrom) == skb_frag_page(lastfrag) && + skb_frag_off(fragfrom) == skb_frag_off(lastfrag) + + skb_frag_size(lastfrag)) { + skb_frag_size_add(lastfrag, todo); + continue; + } + if (unlikely(nr_frags == MAX_SKB_FRAGS)) + return -E2BIG; + skb_frag_page_copy(fragto, fragfrom); + skb_frag_off_copy(fragto, fragfrom); + skb_frag_size_set(fragto, todo); + nr_frags++; + lastfrag = fragto++; + } + } +commit: + WARN_ON_ONCE(len != probe_size); + for (i = 0; i < nr_frags; i++) + skb_frag_ref(to, i); + + skb_shinfo(to)->nr_frags = nr_frags; + to->truesize += probe_size; + to->len += probe_size; + to->data_len += probe_size; + __skb_header_release(to); + return 0; +} + /* Create a new MTU probe if we are ready. * MTU probe is regularly attempting to increase the path MTU by * deliberately sending larger packets. This discovers routing @@ -2395,9 +2446,15 @@ static int tcp_mtu_probe(struct sock *sk) return -1; /* We're allowed to probe. Build it now. */ - nskb = tcp_stream_alloc_skb(sk, probe_size, GFP_ATOMIC, false); + nskb = tcp_stream_alloc_skb(sk, 0, GFP_ATOMIC, false); if (!nskb) return -1; + + /* build the payload, and be prepared to abort if this fails. */ + if (tcp_clone_payload(sk, nskb, probe_size)) { + consume_skb(nskb); + return -1; + } sk_wmem_queued_add(sk, nskb->truesize); sk_mem_charge(sk, nskb->truesize); @@ -2415,7 +2472,6 @@ static int tcp_mtu_probe(struct sock *sk) len = 0; tcp_for_write_queue_from_safe(skb, next, sk) { copy = min_t(int, skb->len, probe_size - len); - skb_copy_bits(skb, 0, skb_put(nskb, copy), copy); if (skb->len <= copy) { /* We've eaten all the data from this skb. -- 2.20.1