From e97269257fe437910cddc7c642a636ca3cf9fb1d Mon Sep 17 00:00:00 2001 From: Jakub Kicinski Date: Tue, 16 Sep 2025 17:09:36 -0700 Subject: net: psp: update the TCP MSS to reflect PSP packet overhead PSP eats 40B of header space. Adjust MSS appropriately. We can either modify tcp_mtu_to_mss() / tcp_mss_to_mtu() or reuse icsk_ext_hdr_len. The former option is more TCP specific and has runtime overhead. The latter is a bit of a hack as PSP is not an ext_hdr. If one squints hard enough, UDP encap is just a more practical version of IPv6 exthdr, so go with the latter. Happy to change. Reviewed-by: Willem de Bruijn Signed-off-by: Jakub Kicinski Signed-off-by: Daniel Zahka Reviewed-by: Eric Dumazet Link: https://patch.msgid.link/20250917000954.859376-10-daniel.zahka@gmail.com Signed-off-by: Paolo Abeni --- include/net/psp/functions.h | 14 ++++++++++++++ include/net/psp/types.h | 3 +++ 2 files changed, 17 insertions(+) (limited to 'include') diff --git a/include/net/psp/functions.h b/include/net/psp/functions.h index 0d7141230f47..183a3c9216b7 100644 --- a/include/net/psp/functions.h +++ b/include/net/psp/functions.h @@ -5,6 +5,7 @@ #include #include +#include #include #include #include @@ -143,6 +144,14 @@ static inline struct psp_assoc *psp_skb_get_assoc_rcu(struct sk_buff *skb) return psp_sk_get_assoc_rcu(skb->sk); } + +static inline unsigned int psp_sk_overhead(const struct sock *sk) +{ + int psp_encap = sizeof(struct udphdr) + PSP_HDR_SIZE + PSP_TRL_SIZE; + bool has_psp = rcu_access_pointer(sk->psp_assoc); + + return has_psp ? psp_encap : 0; +} #else static inline void psp_sk_assoc_free(struct sock *sk) { } static inline void @@ -182,6 +191,11 @@ static inline struct psp_assoc *psp_skb_get_assoc_rcu(struct sk_buff *skb) { return NULL; } + +static inline unsigned int psp_sk_overhead(const struct sock *sk) +{ + return 0; +} #endif static inline unsigned long diff --git a/include/net/psp/types.h b/include/net/psp/types.h index b0e32e7165a3..f93ad0e6c04f 100644 --- a/include/net/psp/types.h +++ b/include/net/psp/types.h @@ -93,6 +93,9 @@ struct psp_dev_caps { #define PSP_MAX_KEY 32 +#define PSP_HDR_SIZE 16 /* We don't support optional fields, yet */ +#define PSP_TRL_SIZE 16 /* AES-GCM/GMAC trailer size */ + struct psp_skb_ext { __be32 spi; u16 dev_id; -- cgit v1.2.3