diff options
| -rw-r--r-- | net/psp/psp_main.c | 39 |
1 files changed, 38 insertions, 1 deletions
diff --git a/net/psp/psp_main.c b/net/psp/psp_main.c index a8534124f626..066222eb56c4 100644 --- a/net/psp/psp_main.c +++ b/net/psp/psp_main.c @@ -166,9 +166,46 @@ static void psp_write_headers(struct net *net, struct sk_buff *skb, __be32 spi, { struct udphdr *uh = udp_hdr(skb); struct psphdr *psph = (struct psphdr *)(uh + 1); + const struct sock *sk = skb->sk; uh->dest = htons(PSP_DEFAULT_UDP_PORT); - uh->source = udp_flow_src_port(net, skb, 0, 0, false); + + /* A bit of theory: Selection of the source port. + * + * We need some entropy, so that multiple flows use different + * source ports for better RSS spreading at the receiver. + * + * We also need that all packets belonging to one TCP flow + * use the same source port through their duration, + * so that all these packets land in the same receive queue. + * + * udp_flow_src_port() is using sk_txhash, inherited from + * skb_set_hash_from_sk() call in __tcp_transmit_skb(). + * This field is subject to reshuffling, thanks to + * sk_rethink_txhash() calls in various TCP functions. + * + * Instead, use sk->sk_hash which is constant through + * the whole flow duration. + */ + if (likely(sk)) { + u32 hash = sk->sk_hash; + int min, max; + + /* These operations are cheap, no need to cache the result + * in another socket field. + */ + inet_get_local_port_range(net, &min, &max); + /* Since this is being sent on the wire obfuscate hash a bit + * to minimize possibility that any useful information to an + * attacker is leaked. Only upper 16 bits are relevant in the + * computation for 16 bit port value because we use a + * reciprocal divide. + */ + hash ^= hash << 16; + uh->source = htons((((u64)hash * (max - min)) >> 32) + min); + } else { + uh->source = udp_flow_src_port(net, skb, 0, 0, false); + } uh->check = 0; uh->len = htons(udp_len); |