github-mirror/linux
1
0
Fork 0
mirror of https://github.com/torvalds/linux.git synced 2026-05-27 00:22:00 +02:00
Code Issues Actions Packages Projects Releases Wiki Activity Graph

Merge branch 'udp-gso-fix-__udp_gso_segment-after-gso_partial-udp-length-change'

Browse Source 
Gal Pressman says:

====================
udp: gso: Fix __udp_gso_segment() after GSO_PARTIAL UDP length change

This series fixes two issues introduced by commit b10b446ce7 ("udp:
gso: Use single MSS length in UDP header for GSO_PARTIAL"), which
switched __udp_gso_segment() to write the single MSS length into the UDP
header for GSO_PARTIAL skbs.

Patch 1 (from Alice) fixes the UDP checksum adjustment in
__udp_gso_segment().
The patch adjusts the checksum by the correct delta, and since msslen
and newlen become equivalent before the loop, drops one of the two
variables to simplify the code.

Patch 2 handles the case where the last segment of a GSO_PARTIAL skb is
itself a GSO skb. This happens when the original packet size is an exact
multiple of MSS, so the post-loop segment is not a remainder skb but a
full GSO chunk and must also carry the single MSS length in its UDP
header.
====================

Link: https://patch.msgid.link/20260518062250.3019914-1-gal@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Jakub Kicinski 2026-05-20 15:04:17 -07:00
commit 9a8e01c500
1 changed files with 8 additions and 14 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

22
net/ipv4/udp_offload.c
View File

@ -482,11 +482,11 @@ struct sk_buff *__udp_gso_segment(struct sk_buff *gso_skb,
struct sock *sk = gso_skb->sk;
unsigned int sum_truesize = 0;
struct sk_buff *segs, *seg;
__be16 newlen, msslen;
struct udphdr *uh;
unsigned int mss;
bool copy_dtor;
__sum16 check;
__be16 newlen;
int ret = 0;
mss = skb_shinfo(gso_skb)->gso_size;
@ -555,15 +555,6 @@ struct sk_buff *__udp_gso_segment(struct sk_buff *gso_skb,
return segs;
}
msslen = htons(sizeof(*uh) + mss);
/* 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;
seg = segs;
uh = udp_hdr(seg);
@ -586,7 +577,7 @@ struct sk_buff *__udp_gso_segment(struct sk_buff *gso_skb,
if (!seg->next)
break;
uh->len = msslen;
uh->len = newlen;
uh->check = check;
if (seg->ip_summed == CHECKSUM_PARTIAL)
@ -599,9 +590,12 @@ struct sk_buff *__udp_gso_segment(struct sk_buff *gso_skb,
uh = udp_hdr(seg);
}
/* last packet can be partial gso_size, account for that in checksum */
newlen = htons(skb_tail_pointer(seg) - skb_transport_header(seg) +
seg->data_len);
/* Unless skb fits perfectly as GSO_PARTIAL, the trailing
* segment may not be full MSS, account for that in the checksum
*/
if (!skb_is_gso(seg))
newlen = htons(skb_tail_pointer(seg) -
skb_transport_header(seg) + seg->data_len);
check = csum16_add(csum16_sub(uh->check, uh->len), newlen);
uh->len = newlen;